[FIX] base: don't unlink base.open_menu but reset it

The ir.actions.todo record base.open_menu is used to redirect the user
to a menu after installing a module.

To do so, a new module override the record changing its action (toward a
menu) and setting its state to "open".

But with f7fe753 when one such changed action is removed after
uninstalling a module (or removing the action by any other way) the
base.open_menu would also be removed. Thus thereafter the open_menu will
not work anymore (since type "automatic" is lost).

With this commit, when whenever base.open_menu is removed, instead its
action will be replaced by base.action_client_base_menu which is the
original action.

closes #11224
related to: #11216, opw-660269

openerp/addons/base/ir/ir_actions.py

@@ -1088,6 +1088,19 @@ Launch Manually Once: after having been launched manually, it sets automatically
     }
     _order="sequence,id"
 
+    @openerp.api.multi
+    def unlink(self):
+        if self:
+            try:
+                todo_open_menu = self.env.ref('base.open_menu')
+                # don't remove base.open_menu todo but set its original action
+                if todo_open_menu in self:
+                    todo_open_menu.action_id = self.env.ref('base.action_client_base_menu').id
+                    self -= todo_open_menu
+            except ValueError:
+                pass
+        return super(ir_actions_todo, self).unlink()
+
     def name_get(self, cr, uid, ids, context=None):
         return [(rec.id, rec.action_id.name) for rec in self.browse(cr, uid, ids, context=context)]