Add null check for 'suggestion' in publish_code_suggestions method in…

… gitlab_provider.py

pr_agent/git_providers/gitlab_provider.py

@@ -327,7 +327,7 @@ def get_relevant_diff(self, relevant_file: str, relevant_line_in_file: str) -> O
     def publish_code_suggestions(self, code_suggestions: list) -> bool:
         for suggestion in code_suggestions:
             try:
-                if 'original_suggestion' in suggestion:
+                if suggestion and 'original_suggestion' in suggestion:
                     original_suggestion = suggestion['original_suggestion']
                 else:
                     original_suggestion = suggestion