[libFuzzer] fix a warning from Wunreachable-code-loop-increment reported by Christian Holler. This also fixes a logical bug, which however does not affect the libFuzzer's ability too much (I wasn't able to create a differentiating test)

git-svn-id: svn://svn.chromium.org/llvm-project/llvm/trunk/lib/Fuzzer@303087 0b72dbe1-c17f-4bc7-b9db-2b4152be0356
1 file changed