fix(sortable): clear savedNodes to fix a leak when items get removed

src/sortable.js

@@ -140,6 +140,14 @@ angular.module('ui.sortable', [])
               }
               savedNodes.appendTo(element);
 
+              // If this is the target connected list then
+              // it's safe to clear the restored nodes since:
+              // update is currently running and
+              // stop is not called for the target list.
+              if(ui.item.sortable.received) {
+                savedNodes = null;
+              }
+
               // If received is true (an item was dropped in from another list)
               // then we add the new item to this list otherwise wait until the
               // stop event where we will know if it was a sort or item was
@@ -173,6 +181,10 @@ angular.module('ui.sortable', [])
                   savedNodes.appendTo(element);
                 }
               }
+
+              // It's now safe to clear the savedNodes
+              // since stop is the last callback.
+              savedNodes = null;
             };
 
             callbacks.receive = function(e, ui) {