Button: adding event.preventDefault. Fixes #5945 - Disabled buttons still allow clicks

(cherry picked from commit 597a313)

Author: shellscape

ui/jquery.ui.button.js

@@ -96,6 +96,7 @@ $.widget( "ui.button", {
 			})
 			.bind( "click.button", function( event ) {
 				if ( options.disabled ) {
+					event.preventDefault();
 					event.stopImmediatePropagation();
 				}
 			});