Fix Flagging entity link template

1. +++ b/flag.module
   @@ -277,13 +277,17 @@ function flag_user_account_removal(UserInterface $account) {
      foreach ($flaggings as $flagging_id => $flagging) {
   -    $flag_service->unflag($flagging->getFlag(), $flagging->getFlaggable(), $account);
   +    if ($flaggable = $flagging->getFlaggable()) {
   +      $flag_service->unflag($flagging->getFlag(), $flaggable, $account);
   +    }
      }
    
      // Remove flags that have been done to this user.
      $flaggings = $flag_service->getFlaggings(NULL, $account);
      foreach ($flaggings as $flagging_id => $flagging) {
   -    $flag_service->unflag($flagging->getFlag(), $flagging->getFlaggable());
   +    if ($flaggable = $flagging->getFlaggable()) {
   +      $flag_service->unflag($flagging->getFlag(), $flaggable);
   +    }
      }
   

   Looks like you have some unrelated local changes in the patch.

2. +++ b/src/Entity/Flagging.php
   @@ -35,7 +35,7 @@ use Drupal\flag\FlaggingInterface;
     *  links = {
   - *    "delete-form" = "flag.confirm_unflag"
   + *    "delete-form" = "/flag/confirm/flag/{flag}/{entity_id}"
   

   A link template can't look like this, drupal doesn't know how to get values for flag/entity_id.

   If this is not possible for some reason (e.g. you don't want to have (flagging) instead in there (which means that links to that will need to load the flagging ID) first then it can't be a link template. You can still get the route directly.

   Note this never worked. You could not have called $flagging->url('delete-form') even before the route => link template conversion (which happened half a year ago, it was just not validated correctly)

   (this is a question to @joachim, not @edurenye).

I'm not sure this is useful for flagging entities, and the right fix here might be in fact to remove it entirely. There's no admin UI for flaggings, there's no 'delete' link when you're editing a flagging. Deleting a flag is done via the unflagging UI instead.

Yeah, agree with that. Patch should remove the links part completely then.

Flag is currently completely broken and can't be installed, so I'd say this is critical :)

Committed.

Thanks everyone!