[FIX] survey: missing questions without section in survey

Since commit https://github.com/odoo/odoo/commit/dba478332681dd21a39c4a183c002b1cf6e046d2, a survey can have questions with no section
associated, which means 'page_ids' field will be empty.

This prevents to display some questions of a survey, as we are
still expecting a structure page/questions. To solve it, we first
append questions with no sections, then all other questions.

closes odoo/odoo#39113

X-original-commit: 149657cfd696e5065b55519927973fa785cc0e22
Signed-off-by: Alex Tuyls <alt-odoo@users.noreply.github.com>

addons/survey/models/survey_survey.py

@@ -298,6 +298,13 @@ class Survey(models.Model):
 
         questions = self.env['survey.question']
 
+        # First append questions without page
+        for question in self.question_ids:
+            if not question.page_id:
+                questions |= question
+
+        # Then, questions in sections
+
         for page in self.page_ids:
             if self.questions_selection == 'all':
                 questions |= page.question_ids
@@ -307,9 +314,6 @@ class Survey(models.Model):
                 else:
                     questions |= page.question_ids
 
-        if not questions:
-            questions = self.question_ids
-
         return questions
 
     def _has_attempts_left(self, partner, email, invite_token):