libpng: Invalid read when handling empty sCAL chunks

The pnghandlesCAL function in pngrutil.c in libpng 1.0.x before 1.0.55, 1.2.x before 1.2.45, 1.4.x before 1.4.8, and 1.5.x before 1.5.4 does not properly handle invalid sCAL chunks, which allows remote attackers to cause a denial of service memory corruption and application crash or possibly have...