libchewing: Heap-buffer-overflow in CheckUserChoose

Detailed report: https://clusterfuzz-external.appspot.com/testcase?key=5228195863330816 Fuzzer: libFuzzerchewingdefaultfuzzer Job Type: libfuzzerasanlibchewing Platform Id: linux Crash Type: Heap-buffer-overflow READ 3 Crash Address: 0x603000004825 Crash State: CheckUserChoose FindInterval Phrasi...