Fix use-of-uninitialized-value introduced in r24700

LOG=N
BUG=chromium:425146
R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/665243002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24760 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/isolate.cc

@@ -66,6 +66,7 @@ ThreadLocalTop::ThreadLocalTop() {
 
 void ThreadLocalTop::InitializeInternal() {
   c_entry_fp_ = 0;
+  c_function_ = 0;
   handler_ = 0;
 #ifdef USE_SIMULATOR
   simulator_ = NULL;