Adds clause to "set_fields" to address bug

Author: DrPaulSharp

RATapi/classlist.py

@@ -318,6 +318,11 @@ def set_fields(self, index: Union[int, slice, str, T], **kwargs) -> None:
         if isinstance(index, (str, self._class_handle)):
             index = self.index(index)
 
+        # Prioritise changing language to avoid CustomFile validator bug
+        value = kwargs.pop("language", None)
+        if value is not None:
+            kwargs = {"language": value, **kwargs}
+
         if importlib.util.find_spec("pydantic"):
             # Pydantic is installed, so set up a context manager that will
             # suppress custom validation errors until all fields have been set.