I'm getting this when trying to convert an RFQ to a real Purchase Order:

Odoo Server Error

Traceback (most recent call last): File "/home/openerp/odoo-8.0-20150115/openerp/http.py", line 525, in _handle_exception return super(JsonRequest, self)._handle_exception(exception) File "/home/openerp/odoo-8.0-20150115/openerp/http.py", line 562, in dispatch result = self._call_function(**self.params) File "/home/openerp/odoo-8.0-20150115/openerp/http.py", line 302, in _call_function return checked_call(self.db, *args, **kwargs) File "/home/openerp/odoo-8.0-20150115/openerp/service/model.py", line 113, in wrapper return f(dbname, *args, **kwargs) File "/home/openerp/odoo-8.0-20150115/openerp/http.py", line 299, in checked_call return self.endpoint(*a, **kw) File "/home/openerp/odoo-8.0-20150115/openerp/http.py", line 791, in __call__ return self.method(*args, **kw) File "/home/openerp/odoo-8.0-20150115/openerp/http.py", line 395, in response_wrap response = f(*args, **kw) File "/home/openerp/odoo-8.0-20150115/openerp/addons/web/controllers/main.py", line 960, in exec_workflow return request.session.exec_workflow(model, id, signal) File "/home/openerp/odoo-8.0-20150115/openerp/http.py", line 1096, in exec_workflow r = self.proxy('object').exec_workflow(self.db, self.uid, self.password, model, signal, id) File "/home/openerp/odoo-8.0-20150115/openerp/http.py", line 867, in proxy_method result = dispatch_rpc(self.service_name, method, args) File "/home/openerp/odoo-8.0-20150115/openerp/http.py", line 114, in dispatch_rpc result = dispatch(method, params) File "/home/openerp/odoo-8.0-20150115/openerp/service/model.py", line 37, in dispatch res = fn(db, uid, *params) File "/home/openerp/odoo-8.0-20150115/openerp/service/model.py", line 113, in wrapper return f(dbname, *args, **kwargs) File "/home/openerp/odoo-8.0-20150115/openerp/service/model.py", line 183, in exec_workflow return exec_workflow_cr(cr, uid, obj, signal, *args) File "/home/openerp/odoo-8.0-20150115/openerp/service/model.py", line 177, in exec_workflow_cr return execute_cr(cr, uid, obj, 'signal_workflow', [res_id], signal)[res_id] File "/home/openerp/odoo-8.0-20150115/openerp/service/model.py", line 159, in execute_cr return getattr(object, method)(cr, uid, *args, **kw) File "/home/openerp/odoo-8.0-20150115/openerp/api.py", line 237, in wrapper return old_api(self, *args, **kwargs) File "/home/openerp/odoo-8.0-20150115/openerp/models.py", line 3491, in signal_workflow result[res_id] = workflow.trg_validate(uid, self._name, res_id, signal, cr) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/__init__.py", line 85, in trg_validate return WorkflowService.new(cr, uid, res_type, res_id).validate(signal) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/service.py", line 91, in validate res2 = wi.validate(signal) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/instance.py", line 75, in validate wi.process(signal=signal, force_running=force_running, stack=stack) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 120, in process ok = self._split_test(activity['split_mode'], signal, stack) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 248, in _split_test self._join_test(t[0], t[1], stack) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 257, in _join_test WorkflowItem.create(self.session, self.record, activity, inst_id, stack=stack) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 95, in create workflow_item.process(stack=stack) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 120, in process ok = self._split_test(activity['split_mode'], signal, stack) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 248, in _split_test self._join_test(t[0], t[1], stack) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 272, in _join_test WorkflowItem.create(self.session, self.record, activity, inst_id, stack=stack) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 95, in create workflow_item.process(stack=stack) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 120, in process ok = self._split_test(activity['split_mode'], signal, stack) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 248, in _split_test self._join_test(t[0], t[1], stack) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 257, in _join_test WorkflowItem.create(self.session, self.record, activity, inst_id, stack=stack) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 95, in create workflow_item.process(stack=stack) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 116, in process if not self._execute(activity, stack): File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 187, in _execute id_new = self.wkf_expr_execute(activity) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 313, in wkf_expr_execute return self.wkf_expr_eval_expr(activity['action']) File "/home/openerp/odoo-8.0-20150115/openerp/workflow/workitem.py", line 291, in wkf_expr_eval_expr result = eval(line, env, nocopy=True) File "/home/openerp/odoo-8.0-20150115/openerp/tools/safe_eval.py", line 313, in safe_eval return eval(c, globals_dict, locals_dict) File "", line 1, in <module> File "/home/openerp/odoo-8.0-20150115/openerp/api.py", line 235, in wrapper return new_api(self, *args, **kwargs) File "/home/openerp/odoo-8.0-20150115/openerp/api.py", line 552, in new_api result = method(self._model, cr, uid, self.ids, *args, **kwargs) File "/home/openerp/odoo-8.0-20150115/openerp/addons/purchase/purchase.py", line 664, in action_invoice_create inv_id = inv_obj.create(cr, uid, inv_data, context=context) File "/home/openerp/odoo-8.0-20150115/openerp/api.py", line 237, in wrapper return old_api(self, *args, **kwargs) File "/home/openerp/odoo-8.0-20150115/openerp/addons/mail/mail_thread.py", line 377, in create thread_id = super(mail_thread, self).create(cr, uid, values, context=context) File "/home/openerp/odoo-8.0-20150115/openerp/api.py", line 237, in wrapper return old_api(self, *args, **kwargs) File "/home/openerp/odoo-8.0-20150115/openerp/api.py", line 332, in old_api result = method(recs, *args, **kwargs) File "/home/openerp/odoo-8.0-20150115/openerp/models.py", line 4007, in create record = self.browse(self._create(old_vals)) File "/home/openerp/odoo-8.0-20150115/openerp/api.py", line 235, in wrapper return new_api(self, *args, **kwargs) File "/home/openerp/odoo-8.0-20150115/openerp/api.py", line 464, in new_api result = method(self._model, cr, uid, *args, **kwargs) File "/home/openerp/odoo-8.0-20150115/openerp/models.py", line 4145, in _create tuple([u[2] for u in updates if len(u) > 2]) File "/home/openerp/odoo-8.0-20150115/openerp/sql_db.py", line 158, in wrapper return f(self, *args, **kwargs) File "/home/openerp/odoo-8.0-20150115/openerp/sql_db.py", line 234, in execute res = self._obj.execute(query, params) ValueError: "null value in column "account_id" violates not-null constraint DETAIL: Failing row contains (4, null, PO00003, 0.00, null, null, null, 1, 1, 1, null, null, 5, null, in_invoice, f, null, null, null, null, null, PO00003, null, null, 2015-01-20 23:32:11.708138, PO00003, 3, 6, null, null, none, 11, draft, f, null, null, 2015-01-20 23:32:11.708138, null, null). " while evaluating u'action_invoice_create()'

I'm guessing this is something accounting related, but what do I need to change/configure?