Effects: Check for anonymous content being exposed via document.activ…

…eElement. Fixes #8288 - Regression: jquery-ui animations focus fix causes Firefox Security Manager veto.

(cherry picked from commit a7e143b)

Conflicts:

	ui/jquery.effects.core.js

ui/jquery.effects.core.js

@@ -370,7 +370,16 @@ $.extend($.effects, {
 				}),
 			active = document.activeElement;
 
-		element.wrap(wrapper);
+		// support: Firefox
+		// Firefox incorrectly exposes anonymous content
+		// https://bugzilla.mozilla.org/show_bug.cgi?id=561664
+		try {
+			active.id;
+		} catch( e ) {
+			active = document.body;
+		}
+
+		element.wrap( wrapper );
 
 		// Fixes #7595 - Elements lose focus when wrapped.
 		if ( element[ 0 ] === active || $.contains( element[ 0 ], active ) ) {