nil value for photoDimension

[colin0brass]

While testing on Windows I saw a couple of times when it failed with a "nil value for photoDimension" on the first run, but I haven't managed to pin that down yet. I haven't seen any such issues on Mac so far.

My best guess is something about initialisation order resulting in a failed read of the exif meta-data, but I haven't proven anything specific yet. So far it has always worked after a retry (or few).