_noop = function(fnMethod) {
				return function() {
					if (this.bIsDestroyed) {
						return undefined;
					}
					if (!this.promiseCache) {
						this.promiseCache = new PromiseCache();
					}
					return fnMethod.apply(this, arguments);
				};
			}
Provides cleanup functionality for the controls promise cache

@private
@param {function} fnExit Existing exit callback function
@returns {function} Returns a thunk applicable to a control prototype, wrapping an existing exit method