Fix for user being able to open multiple "delete posts" modals (#6770)

* Implement fix for multiple fork cards showing

* Fix for admin being able to open multiple 'delete posts' modals

* Fix linting issue

public/src/client/topic/delete-posts.js

@@ -18,6 +18,10 @@ define('forum/topic/delete-posts', ['components', 'postSelect'], function (compo
 	}
 
 	function onDeletePostsClicked() {
+		if (modal) {
+			return;
+		}
+
 		app.parseAndTranslate('partials/delete_posts_modal', {}, function (html) {
 			modal = html;