OSV-2020-1647 UNKNOWN READ in aiTexture::~aiTexture

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=25108 Crash type: UNKNOWN READ Crash state: aiTexture::aiTexture Assimp::MDLImporter::SkipSkinLump3DGSMDL7 Assimp::HMPImporter::ReadFirstSkin...