core.files.images.get_image_dimensions broken

[artscoop]

Each time you access a model instance which contains an ImageField, core.files.images.get_image_dimensions is called. I have always found it overkill but whatever.
The bug is that the function chokes because get_image_dimensions returns None on a valid image (which is a 1x1 BMP32ARGB, not recognized by Pillow).
I end with a

>> return self._get_image_dimensions()[0]
TypeError: 'NoneType' object has no attribute '__getitem__'

When hitting an unrecognized image file, the function should still return a tuple like (0, 0) or (-1, -1) (but it returns None). I changed the function code to this:

    from PIL import Image
    try:
        image = Image.open(file_or_path)
        return image.size  # raster data is not loaded here
    except IOError:
        return [-1, -1]

what do you think ? It appears as a bug to me.