graphicsmagick:coder_MAT_fuzzer: Use-of-uninitialized-value in IsGrayImage

Project: http://hg.code.sf.net/p/graphicsmagick/code Detailed Report: https://oss-fuzz.com/testcase?key=5147972366303232 Project: graphicsmagick Fuzzing Engine: libFuzzer Fuzz Target: coderMATfuzzer Job Type: libfuzzermsangraphicsmagick Platform Id: linux Crash Type: Use-of-uninitialized-value...