Release build fix

TBR=rossberg@chromium.org
BUG=

Review URL: https://codereview.chromium.org/14296008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14287 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/runtime.cc

@@ -813,6 +813,7 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_TypedArrayInitialize) {
       break;
     default:
       UNREACHABLE();
+      return NULL;
   }
 
   holder->set_buffer(*buffer);