Do not use a message branch if no msg id provided to prompt tracer

src/khoj/processor/conversation/utils.py

@@ -423,6 +423,7 @@ def commit_conversation_trace(
         msg_branch = f"m_{mid}" if mid else None
         if msg_branch and msg_branch not in repo.branches:
             repo.create_head(msg_branch)
+        if msg_branch:
             repo.heads[msg_branch].checkout()
 
         # Include file with content to commit