Handle panics that percolate up to the graceful module (#11291)

Handle panics that percolate up to the graceful module (#11291)

* Handle panics in graceful goroutines

Adds a some deferred functions to handle panics in graceful goroutines

Signed-off-by: Andrew Thornton <art27@cantab.net>
* Handle panic in webhook.Deliver

Signed-off-by: Andrew Thornton <art27@cantab.net>
* Handle panic in mirror.syncMirror

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>