Validate shift bit depths in `png_set_shift` to prevent infinite loop
Validate shift bit depths in `png_set_shift` to prevent infinite loop
Add missing NULL pointer checks in four public API functions
Add missing NULL pointer checks in four public API functions
Fix two copy-paste typos in colormap read and sPLT write
Fix two copy-paste typos in colormap read and sPLT write
Fix wrong channel indices in `png_image_read_and_map` RGB_ALPHA path
Fix wrong channel indices in `png_image_read_and_map` RGB_ALPHA path