Merge pull request #4039 from themrzmaster/main

fix tool usage null content using vertexai

litellm/llms/vertex_ai.py

@@ -647,9 +647,9 @@ def completion(
 
         prompt = " ".join(
             [
-                message["content"]
+                message.get("content")
                 for message in messages
-                if isinstance(message["content"], str)
+                if isinstance(message.get("content", None), str)
             ]
         )