Optimizing: Clean up after HRor.

Change-Id: I96bd7fa2e8bdccb87a3380d063dad0dd57fed9d7
diff --git a/compiler/optimizing/code_generator_x86_64.cc b/compiler/optimizing/code_generator_x86_64.cc
index 610ce67..1fee192 100644
--- a/compiler/optimizing/code_generator_x86_64.cc
+++ b/compiler/optimizing/code_generator_x86_64.cc
@@ -3755,6 +3755,7 @@
     }
     default:
       LOG(FATAL) << "Unexpected operation type " << op->GetResultType();
+      UNREACHABLE();
   }
 }