🪲 Old programs without 'is_modified' are shown (#5521)

Also fixes that only modified programs are shown in 'My public profile'

**How to test**
Is it correct that we don't have saved programs in the test database? Then it's a bit difficult to test:
1. Go to programs.py and comment out line 101, 104 and 106
2. Save a few programs, check if they are shown in `/my-programs`
3. Make a few public and see if they are shown in 'My public profile'

app.py

@@ -1042,7 +1042,9 @@ def programs_page(user):
         date = utils.delta_timestamp(item['date'])
         # This way we only keep the first 4 lines to show as preview to the user
         preview_code = "\n".join(item['code'].split("\n")[:4])
-        if item.get('is_modified'):
+        # When saving a program, 'is_modified' is set to True or False
+        # But for older programs, 'is_modified' doesn't exist yet, therefore the check
+        if item.get('is_modified') or 'is_modified' not in item:
             programs.append(
                 {'id': item['id'],
                  'preview_code': preview_code,
@@ -2667,10 +2669,15 @@ def public_user_page(username):
                                                            public=True,
                                                            pagination_token=page)
 
+        modified_programs = []
+        for program in all_programs:
+            if program.get('is_modified') or 'is_modified' not in program:
+                modified_programs.append(program)
+
         sorted_level_programs = hedy_content.Adventures(
-            g.lang).get_sorted_level_programs(all_programs, adventure_names)
+            g.lang).get_sorted_level_programs(modified_programs, adventure_names)
         sorted_adventure_programs = hedy_content.Adventures(
-            g.lang).get_sorted_adventure_programs(all_programs, adventure_names)
+            g.lang).get_sorted_adventure_programs(modified_programs, adventure_names)
 
         favorite_program = None
         if 'favourite_program' in user_public_info and user_public_info['favourite_program']:

website/programs.py

@@ -103,7 +103,7 @@ def store_user_program(self,
         # and if it was already modified and now is so again, count should not increase.
         if is_modified and not program.get('is_modified'):
             self.db.increase_user_program_count(user["username"])
-            program = self.db.update_program(program['id'], {'is_modified': True})
+        program = self.db.update_program(program['id'], {'is_modified': is_modified})
 
         querylog.log_value(program_id=program['id'],
                            adventure_name=adventure_name, error=error, code_lines=len(code.split('\n')))