Fix `cache_handle` problem when webhook fail
Fix `cache_handle` problem when webhook fail

When the case is eligible for webhook, but the webhook failed (due to, for example, timeout, or server error), an exception is throw on line 255 due to missing `cache_handle`. 
This patch fix the issue.
ZeChrales/Monocle,sebast1219/Monocle,RobTwoThree/Monocle,tallypokemap/Monocle,ZeChrales/Monocle,DavisPoGo/Monocle,tallypokemap/Monocle,evenly-epic-mule/Monocle,DavisPoGo/Monocle,evenly-epic-mule/Monocle,DavisPoGo/Monocle,RobTwoThree/Monocle,ZeChrales/Monocle,sebast1219/Monocle,sebast1219/Monocle,tallypokemap/Monocle,evenly-epic-mule/Monocle,RobTwoThree/Monocle,RobTwoThree/Monocle