API: Relax multimodal format, fixes HuggingFace Chat UI (#6353)

extensions/openai/completions.py

@@ -154,8 +154,9 @@ def convert_history(history):
                     elif item['type'] == 'text' and isinstance(item['text'], str):
                         content = item['text']
 
-                if image_url and content:
+                if image_url:
                     new_history.append({"image_url": image_url, "role": "user"})
+                if content:
                     new_history.append({"content": content, "role": "user"})
             else:
                 new_history.append(entry)