perf(claude): ensure system message removed (#867) (#1255)

Author: RockChinQ

pkg/provider/modelmgr/requesters/anthropicmsgs.py

@@ -59,9 +59,11 @@ async def call(
             if m.role == "system":
                 system_role_message = m
 
-                messages.pop(i)
                 break
 
+        if system_role_message:
+            messages.pop(i)
+
         if isinstance(system_role_message, llm_entities.Message) \
             and isinstance(system_role_message.content, str):
             args['system'] = system_role_message.content