Widget: Set event.target in ._trigger(). Fixes #7852 - Droppable event target changes under jQuery 1.7.

(cherry picked from commit 1b165148a6)

ui/jquery.ui.widget.js

@@ -257,6 +257,10 @@ $.Widget.prototype = {
 			}
 		}
 
+		// the original event may come from any element
+		// so we need to reset the target on the new event
+		event.target = this.element[0];
+
 		this.element.trigger( event, data );
 
 		return !( $.isFunction(callback) &&