Fix crash when opening .ora images caused by MDI changes.
Fix crash when opening .ora images caused by MDI changes.

[Fixes bug #671540]

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