Monochrome TIFF files not loadable if optional BitsPerSample tag missing

When attempting to load a monochrome TIFF image (dolphin preview, kolourpaint, or any other KDE-base application), a message stating "Unable to load, invalid image format" (or no preview, or similar message) is displayed if the image file is missing the BitsPerSample TIFF tag. This tag is optional in monochrome images, with a default value of '1'. Adding the tag with the correct value causes the images to be displayed/load properly.

Downgrading from qt 4.6 to qt 4.5.3 solves the issue.