OSV-2020-867 Heap-buffer-overflow in icu_64::CollationIterator::appendCEsFromCE32

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15613 Crash type: Heap-buffer-overflow READ 4 Crash state: icu64::CollationIterator::appendCEsFromCE32 icu64::DataBuilderCollationIterator::fetchCEs icu64::CollationDataBuilder::getCEs...