Don't handle filesystem watcher callbacks once texture viewer is closed
Don't handle filesystem watcher callbacks once texture viewer is closed

* Fixes a reported crash

michaelrgb/renderdoc,cgmb/renderdoc,googlestadia/renderdoc,Lssikkes/renderdoc,Lssikkes/renderdoc,baldurk/renderdoc,TurtleRockStudios/renderdoc_public,TurtleRockStudios/renderdoc_public,michaelrgb/renderdoc,etnlGD/renderdoc,Velro/renderdoc,googlestadia/renderdoc,baldurk/renderdoc,cgmb/renderdoc,etnlGD/renderdoc,Lssikkes/renderdoc,baldurk/renderdoc,michaelrgb/renderdoc,Zorro666/renderdoc,baldurk/renderdoc,TurtleRockStudios/renderdoc_public,victor-moya/renderdoc,Velro/renderdoc,googlestadia/renderdoc,michaelrgb/renderdoc,michaelrgb/renderdoc,Zorro666/renderdoc,baldurk/renderdoc,Zorro666/renderdoc,etnlGD/renderdoc,Yours3lf/renderdoc,victor-moya/renderdoc,Yours3lf/renderdoc,Velro/renderdoc,etnlGD/renderdoc,Lssikkes/renderdoc,Lssikkes/renderdoc,Yours3lf/renderdoc,cgmb/renderdoc,etnlGD/renderdoc,victor-moya/renderdoc,googlestadia/renderdoc,Velro/renderdoc,Zorro666/renderdoc,Yours3lf/renderdoc,victor-moya/renderdoc,googlestadia/renderdoc,baldurk/renderdoc,Lssikkes/renderdoc,googlestadia/renderdoc,cgmb/renderdoc,Yours3lf/renderdoc,Zorro666/renderdoc,Yours3lf/renderdoc,cgmb/renderdoc,Velro/renderdoc,Velro/renderdoc,etnlGD/renderdoc,Zorro666/renderdoc,victor-moya/renderdoc,TurtleRockStudios/renderdoc_public,victor-moya/renderdoc,TurtleRockStudios/renderdoc_public,TurtleRockStudios/renderdoc_public