Improved custom homepage check on item deletion

Custom homepage usage will now be checked before any actioning
of deletion rather than potentially causing an exception acting
during the deletion.

Previously a deletion could still be created, within the recycle bin,
for the parent which may lead to the page being deleted anyway.

For #3150

app/Entities/Models/Entity.php

@@ -36,6 +36,7 @@ use Illuminate\Database\Eloquent\SoftDeletes;
  * @property string     $slug
  * @property Carbon     $created_at
  * @property Carbon     $updated_at
+ * @property Carbon     $deleted_at
  * @property int        $created_by
  * @property int        $updated_by
  * @property bool       $restricted