Sortable: Make sure we have a placeholder before trying to remove it …

…during a cancel. Fixes #6879 - Sortable: Calling cancel when there is no sort occurring throws an error.

(cherry picked from commit f165c93)

ui/jquery.ui.sortable.js

@@ -378,21 +378,23 @@ $.widget("ui.sortable", $.ui.mouse, {
 
 		}
 
-		//$(this.placeholder[0]).remove(); would have been the jQuery way - unfortunately, it unbinds ALL events from the original node!
-		if(this.placeholder[0].parentNode) this.placeholder[0].parentNode.removeChild(this.placeholder[0]);
-		if(this.options.helper != "original" && this.helper && this.helper[0].parentNode) this.helper.remove();
-
-		$.extend(this, {
-			helper: null,
-			dragging: false,
-			reverting: false,
-			_noFinalSort: null
-		});
+		if (this.placeholder) {
+			//$(this.placeholder[0]).remove(); would have been the jQuery way - unfortunately, it unbinds ALL events from the original node!
+			if(this.placeholder[0].parentNode) this.placeholder[0].parentNode.removeChild(this.placeholder[0]);
+			if(this.options.helper != "original" && this.helper && this.helper[0].parentNode) this.helper.remove();
+
+			$.extend(this, {
+				helper: null,
+				dragging: false,
+				reverting: false,
+				_noFinalSort: null
+			});
 
-		if(this.domPosition.prev) {
-			$(this.domPosition.prev).after(this.currentItem);
-		} else {
-			$(this.domPosition.parent).prepend(this.currentItem);
+			if(this.domPosition.prev) {
+				$(this.domPosition.prev).after(this.currentItem);
+			} else {
+				$(this.domPosition.parent).prepend(this.currentItem);
+			}
 		}
 
 		return this;