Prevent 500 if hook url is down when testing a hook, fixes #7376
Created by: Razer6
What does this MR do?
This PR catches errors if the target webhook url is not down. If so, an error message is displayed at the bottom of the page.
Why was this MR needed?
Currently, if the user adds a webhook URL which is down, a 500 error is raised when pressing the Test Hook button.
What are the relevant issue numbers / Feature requests?
This PR fixes #7376 (closed)