Fix #1434928 - Auto Crop now uses the flattened image, not the current layer.
Fix #1434928 - Auto Crop now uses the flattened image, not the current layer.

PintaProject/Pinta,jakeclawson/Pinta,Fenex/Pinta,PintaProject/Pinta,Mailaender/Pinta,jakeclawson/Pinta,Mailaender/Pinta,Fenex/Pinta,PintaProject/Pinta