OSV-2018-288 Use-of-uninitialized-value in jbig2_decode_symbol_dict

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=9688 Crash type: Use-of-uninitialized-value Crash state: jbig2decodesymboldict jbig2symboldictionary jbig2parsesegment...