Harden the tiff reader.
Harden the tiff reader.

When trying to parse a file with the tiff reader, if it parses somewhat
but reports no samples per pixel, the reader was raising a TypeError.
This caused Girder to fail to move to the next possible tile source.

girder/large_image,girder/large_image,DigitalSlideArchive/large_image,DigitalSlideArchive/large_image,DigitalSlideArchive/large_image,girder/large_image