Error when canceling deletion of map

[Zehra]

It seems when canceling a maps deletion, it leads to a generic error. By pressing the delete button, it will request confirmation to delete or to cancel. If cancel is press, it leads to generic error.

[allejo]

Moving this 0.10.x so it's not blocking the 0.10.0 release.

The call to HTMLController::getPreviousUrl() makes use of $this->getRequest()->get('previous_paths'). When a page has a non-existent link, such as a link to an asset that could not be found, that'll get pushed up to the beginning of the returned array and cause this issue.

One of two fixes are needed here (or both):

1. Don't render broken URLs to assets (currently a broken URL is being rendered for an unknown team).

   As an example, /dev.php/assets/imgs/team_.png is being generated as an avatar for a broken team.

2. Check if the first previous_url is a valid URL in HTMLController::getPreviousUrl()