fix empty part checking

autogen/oai/gemini.py

@@ -501,7 +501,12 @@ def is_function_call(parts):
             # If this is first message or the role is different from the previous role then append the parts
             else:
                 # If the previous text message is empty then update the text to "empty" as Gemini does not support empty messages
-                if (len(rst) > 0) and ("text" in rst[-1].parts[0]._raw_part) and (rst[-1].parts[0].text == ""):
+                if (
+                    (len(rst) > 0)
+                    and hasattr(rst[-1].parts[0], "_raw_part")
+                    and hasattr(rst[-1].parts[0]._raw_part, "text")
+                    and (rst[-1].parts[0].text == "")
+                ):
                     append_text_to_last("empty")
                 append_parts(parts, role)