OSV-2020-730 Use-of-uninitialized-value in xmlOutputBufferWriteEscape

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15914 Crash type: Use-of-uninitialized-value Crash state: xmlOutputBufferWriteEscape xmlNodeDumpOutput xsltSaveResultTo...