do not crash when using invalid images (e.g. pdf renamed to jpg)
do not crash when using invalid images (e.g. pdf renamed to jpg)

winzard/django-image-cropping,henriquechehad/django-image-cropping,winzard/django-image-cropping,winzard/django-image-cropping,henriquechehad/django-image-cropping,henriquechehad/django-image-cropping