stb_image is a single file MIT licensed library for processing images. If `stbi__load_gif_main` in `stbi_load_gif_from_memory` fails it returns a null pointer and may keep the `z` variable uninitialized. In case the caller also sets the flip vertically flag, it continues and calls `stbi__vertical_flip_slices` with the null pointer result value and the uninitialized `z` value. This may result in a program crash.
https://securitylab.github.com/advisories/GHSL-2023-145_GHSL-2023-151_stb_image_h/
https://github.com/nothings/stb/blob/5736b15f7ea0ffb08dd38af21067c314d6a3aae9/stb_image.h#L1448