Leaving and Navigating to Deleted Tasks

When a task is deleted it is expected that it can't be accessed anymore.

What is not expected is the way how this is presented in the following situations:

1. When trying to leave a deleted task via 'Back to task list' button, an error message pops up and you can't leave the task editor.
   Suggestion: Leave the editor and present feedback in the main screen, e.g. the normal 'Successfully left' or 'Task has been deleted in the meantime'
2. When invoking translate5 through a task edit URL of a deleted task, it won't load but show an application error.
   Suggestion: Redirect to main screen and present feedback 'Task #$id has been deleted'