this._changeHandlers was undefined when calling cancel()

store.js

@@ -115,7 +115,7 @@ assign(Store.prototype, {
 			cancel: function() {
 				var index = this._changeHandlers.indexOf(callback);
 				if (~index) this._changeHandlers.splice(index, 1);
-			}
+			}.bind(this)
 		};
 	},
 
@@ -163,4 +163,4 @@ assign(Store.prototype, {
 	}
 });
 
-export { Store };
+export { Store };