Do image availability check only on iOS 8-
Do image availability check only on iOS 8-

This prevents warnings.

Current implementation is a bit of a hacky workaround. But since we plan to drop iOS 7 next release I'm okay with that for now.

mac-cain13/R.swift,mac-cain13/R.swift,ntnmrndn/R.swift,renrawnalon/R.swift,tomasharkema/R.swift,renrawnalon/R.swift,tomasharkema/R.swift,mac-cain13/R.swift,ntnmrndn/R.swift