[FIX] project: fix the traceback when group by project in the planning

Steps:
- Open Field service
- Select planning then by user
- Group by project
- The trace back is coming

Issue:
- when we trying to group by projects the trace back is raised.

Cause:
- In  '_search_on_comodel' method filtered_domain does't set perfectly,
  The filtered_domain it is not set for the additional_domain , when we
  given on additional_domain, on that time filter_domain does not consider
  the additional_domain, because of that traceback will be coming.

Fix:
- By adding an 'if' condition for cases when you provide an additional
  domain, it will work fine.

task-3522178

closes odoo/odoo#140661

Related: odoo/enterprise#48652
Signed-off-by: Xavier Bol (xbo) <xbo@odoo.com>

addons/project/models/project_task.py

@@ -1161,11 +1161,9 @@ class Task(models.Model):
             f"{field}.id": "id",
             f"{field}.name": "name",
         })
-        if not filtered_domain:
-            return False
         if additional_domain:
-            filtered_domain = expression.AND([filtered_domain, additional_domain])
-        return self.env[comodel].search(_change_operator(filtered_domain), order=order)
+            filtered_domain = expression.AND([_change_operator(filtered_domain), additional_domain])
+        return self.env[comodel].search(filtered_domain, order=order) if filtered_domain else False
 
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