_wrap_g_file_load_contents_async doesn't increment the refcounts of notify->callback and notify->data, so the objects tend to get garbage collected while the operation is in progress.  Adding Py_INCREF(notify->callback) and Py_XINCREF(notify->data) as seen in most other async method wrappers makes everything behave sanely.

I noticed this while trying to use file.load_contents_async, but it also affects a few other file async methods: append_to_async, create_async, replace_async, query_info_async.  I checked the other .override files and found no other async method wrappers that didn't increment these refcounts.