backend: Filter out invalid message text when generating chat history (#862)

Filter out invalid message text

Author: tianjing-li

src/backend/chat/custom/custom.py

@@ -90,6 +90,7 @@ async def chat(
                 "status_code": 500,
             }
 
+
     def is_final_event(
         self, event: Dict[str, Any], chat_request: CohereChatRequest
     ) -> bool:

src/backend/chat/custom/tool_calls.py

@@ -71,6 +71,7 @@ async def _call_all_tools_async(
         )
 
 
+
 async def _call_tool_async(
     ctx: Context,
     db: Session,

src/backend/services/chat.py

@@ -471,7 +471,8 @@ def create_chat_history(
     chat_request: BaseChatRequest,
 ) -> list[ChatMessage]:
     """
-    Create chat history from conversation messages or request.
+    Create chat history from conversation messages or request, this chat history
+    is sent to the chat SDK call for added context.
 
     Args:
         conversation (Conversation): Conversation object.
@@ -487,11 +488,13 @@ def create_chat_history(
     if conversation.messages is None:
         return []
 
-    # Don't include the user message that was just sent
+    # Filter out user message that was just sent
+    # And any empty messages
     text_messages = [
         message
         for message in conversation.messages
         if message.position < user_message_position
+        and message.text
     ]
     return [
         ChatMessage(