[5.10] Fixed JS issue with element deletion blockers after filtering

[nfourtythree]

Description

Noticed when registering deletion blockers and some getting filtered out that the array keys could become non-sequential e.g. 0, 2, 3

This meant the following JS would not work as expected and showed the confirm delete dialog instead of the blockers modal.

      if (!data.blockers.length) {
        await this.confirmAndDelete(data.totalElements);
        return;
      }