fix nodes ReAct agent file input missing

nodes_react_agent.py

@@ -86,7 +86,7 @@ class NodesReActAgent:
 
         print(f"ReActAgent initialized with {provider} - {model}.")
 
-    def __call__(self, question: str, input_file: str) -> str:
+    def __call__(self, question: str, input_file: str = "") -> str:
         input_msg = [HumanMessage(content=question)]
         out = self.react_graph.invoke({"messages": input_msg, "input_file": input_file})