[clang-format] Fix the crash when formatting unsupported encodings

Fixes PR33946

Differential Revision: https://reviews.llvm.org/D61559

git-svn-id: svn://svn.chromium.org/llvm-project/cfe/trunk/tools/clang-format@360257 0b72dbe1-c17f-4bc7-b9db-2b4152be0356
1 file changed