gs-page: Own job instance in helper
The job can be freed before the code goes to the place of the gs_page_helper_free(), which causes a use after free. That can be seen when an app update is cancelled before it's finished.
The job can be freed before the code goes to the place of the gs_page_helper_free(), which causes a use after free. That can be seen when an app update is cancelled before it's finished.