Avoid buffer->move_to() in case of buffer error Fixes https://github.com/behdad/harfbuzz/issues/223 Right now we cannot test this because it has to be tested using hb-fuzzer. We should move all fuzzing tests from test/shaping/tests/fuzzed.tests to test/fuzzing/ and have its own test runner. At that point, should add test from this issue as well.