fix mcp error not input (#22505)

Signed-off-by: kenwoodjw <blackxin55+@gmail.com>

api/core/mcp/server/streamable_http.py

@@ -148,9 +148,7 @@ class MCPServerStreamableHTTPRequestHandler:
         if not self.end_user:
             raise ValueError("User not found")
         request = cast(types.CallToolRequest, self.request.root)
-        args = request.params.arguments
+        args = request.params.arguments or {}
-        if not args:
-            raise ValueError("No arguments provided")
         if self.app.mode in {AppMode.WORKFLOW.value}:
             args = {"inputs": args}
         elif self.app.mode in {AppMode.COMPLETION.value}: