Gimp: gimp: stack buffer overflow in pnmscanner_gettoken()

A flaw was found in GIMP's PNM file format parser. When parsing a specially crafted PNM file, the pnmscanner_gettoken() function writes a null terminator one byte past the end of a stack-allocated buffer due to an off-by-one error in the loop boundary check. This could lead to memory corruption, potentially resulting in denial of service or arbitrary code execution.