Fix handling of context creation failure since r13978.

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 58b2ad0387b4bf50b439e437bdea75fb1b760ff1..ce58a86cf5de1e8fbc529a3fbe9a3522b137ffe0 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -303,9 +303,9 @@ Handle<Context> Bootstrapper::CreateEnvironment(
     v8::ExtensionConfiguration* extensions) {
   HandleScope scope(isolate_);
   Genesis genesis(isolate_, global_object, global_template, extensions);
-  Handle<Object> context(isolate_->global_handles()->Create(*genesis.result()));
-  Handle<Context> env = Handle<Context>::cast(context);
-  if (!env.is_null()) {
+  if (!genesis.result().is_null()) {
+    Handle<Object> ctx(isolate_->global_handles()->Create(*genesis.result()));
+    Handle<Context> env = Handle<Context>::cast(ctx);
     if (InstallExtensions(env, extensions)) {
       return env;
     }