ImageMagick: MSL image stack index may fail to refresh, leading to leaked images

Sometimes msl.c fails to update the stack index, so an image is stored in the wrong slot and never freed on error, causing leaks. ==841485==ERROR: LeakSanitizer: detected memory leaks Direct leak of 13512 bytes in 1 objects allocated from: 0 0x7ff330759887 in interceptormalloc...