Accordion - Make sure we have an element before trying to modify the className. Fixes #6856 - Accordion: Opening a panel after all panels have been collapsed causes an error.

Author: scottgonzalez

ui/jquery.ui.accordion.js

@@ -504,7 +504,9 @@ $.widget( "ui.accordion", {
 		// other classes are removed before the animation; this one needs to stay until completed
 		this.toHide.removeClass( "ui-accordion-content-active" );
 		// Work around for rendering bug in IE (#5421)
-		this.toHide.parent()[0].className = this.toHide.parent()[0].className;
+		if ( this.toHide.length ) {
+			this.toHide.parent()[0].className = this.toHide.parent()[0].className;
+		}
 
 		this._trigger( "change", null, this.data );
 	}