Protect against API abuse.

src/api.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 6273 matching lines @@
     StackTrace::StackTraceOptions options) {
   i::Isolate::Current()->SetCaptureStackTraceForUncaughtExceptions(
       capture,
       frame_limit,
       options);
 }
 
 
 void V8::SetCounterFunction(CounterLookupCallback callback) {
   i::Isolate* isolate = i::Isolate::UncheckedCurrent();
+  // TODO(svenpanne) The Isolate should really be a parameter.
+  if (isolate == NULL) return;
   isolate->stats_table()->SetCounterFunction(callback);
 }
 
 
 void V8::SetCreateHistogramFunction(CreateHistogramCallback callback) {
   i::Isolate* isolate = i::Isolate::UncheckedCurrent();
+  // TODO(svenpanne) The Isolate should really be a parameter.
+  if (isolate == NULL) return;
   isolate->stats_table()->SetCreateHistogramFunction(callback);
   isolate->InitializeLoggingAndCounters();
   isolate->counters()->ResetHistograms();
 }
 
 
 void V8::SetAddHistogramSampleFunction(AddHistogramSampleCallback callback) {
   i::Isolate* isolate = i::Isolate::UncheckedCurrent();
+  // TODO(svenpanne) The Isolate should really be a parameter.
+  if (isolate == NULL) return;
   isolate->stats_table()->
       SetAddHistogramSampleFunction(callback);
 }
 
 void V8::SetFailedAccessCheckCallbackFunction(
     FailedAccessCheckCallback callback) {
   i::Isolate* isolate = i::Isolate::Current();
   isolate->SetFailedAccessCheckCallback(callback);
 }
 
@@ skipping 1290 matching lines @@
   Isolate* isolate = reinterpret_cast<Isolate*>(info.GetIsolate());
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 } }  // namespace v8::internal