TinyMCE, floating toolbars: return early if no selected element in the editor. See #30619.

git-svn-id: https://develop.svn.wordpress.org/trunk@31727 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/js/tinymce/plugins/wordpress/plugin.js

@@ -585,6 +585,10 @@ tinymce.PluginManager.add( 'wordpress', function( editor ) {
 					margin = 8,
 					adminbarHeight = 0;
 
+				if ( ! currentSelection ) {
+					return;
+				}
+
 				windowPos = window.pageYOffset || document.documentElement.scrollTop;
 				adminbar = tinymce.$( '#wpadminbar' )[0];
 				mceToolbar = tinymce.$( '.mce-toolbar-grp', editor.getContainer() )[0];