fixed: resize dialogue still pops up when uploading images

Quick follow up on this issue: https://github.com/wordpress-mobile/WordPress-iOS/commit/7955c4a71eb2995e763cf0671a3d6db0eb0833a6

Koke's fix almost worked, all we needed was a property and an additional check before the resize sheet is shown. Works fine now on iPads running iOS 6 and iOS 7

PS:
This is my first ever pull request (or contribution)... I hope I've done this correctly - let me know if I haven't, or if you need more info.