JPEG segment size not validated

Using my AFL-based fuzzer for Java, Kelinci (https://github.com/isstac/kelinci) I found that a NegativeArraySizeException may be throw when attempting to read an invalid JPEG image.

Each JPEG segment starts with a two-byte unsigned integer specifying the segment size. Segments are parsed by org.apache.commons.imaging.formats.jpeg.JpegUtils.traverseJFIF(). As the specified size includes these two bytes, the method subtracts 2 from the size before it is used. It then attempts to allocate a buffer for the segment, which fails if the specified size is 0 or 1. The method should throw an ImageReadException instead.