Fix forEach typo

This one broke sanbox and crazy-slots, introduced in [this commit](https://github.com/alohaeditor/Aloha-Editor/commit/400e22e0bd558ccdf53d35ba84d84749685a71d2#diff-c3ba2f10bd605d37093f207c79021c5bR142), @deliminator please review if this is what you meant.