fix: handling empty attachment field (#1351)

Author: sjd9021

python/composio/tools/toolset.py

@@ -669,13 +669,15 @@ def _substitute_file_uploads_recursively(
             return request
 
         params = schema["properties"]
-        for _param in request:
+        params_to_process = list(request.keys())
+        for _param in params_to_process:
             if _param not in params:
                 continue
 
             if self._file_uploadable(schema=params[_param]):
                 # skip if the file is not provided
                 if request[_param] is None or request[_param] == "":
+                    del request[_param]
                     continue
 
                 request[_param] = FileUploadable.from_path(