Plug a unit test memory leak.

MatchFinder.addMatcher doesn't take ownership.

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@217162 91177308-0d34-0410-b5e6-96231b3b80d8
Don't write files with no fixes.

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@217163 91177308-0d34-0410-b5e6-96231b3b80d8