Fix workout template edit saved snackbar exception when navigated to another page and dismissed.

[cherking19]

• Make and save an edit to a workout template
• The page will go back and the Edit Success snackbar will appear
• If you go to another page while the snackbar is still displayed, clicking the OK button:
• RESULT: of the snackbar will throw an exception and the snackbar will not be dismissed
• EXPECTED: the snackbar will safely be dismissed

This is not the case with the 'Workout already being tracked' snackbar, so a solution may be found by inspecting its behavior

[cherking19]

https://stackoverflow.com/questions/54617432/looking-up-a-deactivated-widgets-ancestor-is-unsafe