Fixed an issue with the legacy toolbar under iOS 8.

Fixes [this bug](https://github.com/wordpress-mobile/WordPress-iOS/issues/2597).

Can be tested in WPiOS branch `issue/2597-editor-locking-up` which is set up to use the latest commit from issue/wpios-2597-editor-locking-up (just check it out and `pod install`).

/cc @aerych