OSV-2018-82 Heap-buffer-overflow in OT::LigatureSubstFormat1::closure

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=10081 Crash type: Heap-buffer-overflow READ 8 Crash state: OT::LigatureSubstFormat1::closure hbvoidt const OT::hbclosurecontextt::dispatch OT::hbclosurecontextt::returnt OT::LigatureSubst::dispatchOT::hbclosureco...