Fix crash in ScriptDebugServer::setBreakpoint

Source/bindings/v8/ScriptDebugServer.cpp

 /*
  * Copyright (c) 2010-2011 Google Inc. 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
@@ skipping 82 matching lines @@
 
     v8::Local<v8::Object> info = v8::Object::New(m_isolate);
     info->Set(v8AtomicString(m_isolate, "sourceID"), v8String(debuggerContext->GetIsolate(), sourceID));
     info->Set(v8AtomicString(m_isolate, "lineNumber"), v8::Integer::New(debuggerContext->GetIsolate(), scriptBreakpoint.lineNumber));
     info->Set(v8AtomicString(m_isolate, "columnNumber"), v8::Integer::New(debuggerContext->GetIsolate(), scriptBreakpoint.columnNumber));
     info->Set(v8AtomicString(m_isolate, "interstatementLocation"), v8Boolean(interstatementLocation, debuggerContext->GetIsolate()));
     info->Set(v8AtomicString(m_isolate, "condition"), v8String(debuggerContext->GetIsolate(), scriptBreakpoint.condition));
 
     v8::Handle<v8::Function> setBreakpointFunction = v8::Local<v8::Function>::Cast(m_debuggerScript.newLocal(m_isolate)->Get(v8AtomicString(m_isolate, "setBreakpoint")));
     v8::Handle<v8::Value> breakpointId = v8::Debug::Call(setBreakpointFunction, info);
-    if (!breakpointId->IsString())
+    if (breakpointId.IsEmpty() || !breakpointId->IsString())
         return "";
     *actualLineNumber = info->Get(v8AtomicString(m_isolate, "lineNumber"))->Int32Value();
     *actualColumnNumber = info->Get(v8AtomicString(m_isolate, "columnNumber"))->Int32Value();
     return toCoreString(breakpointId.As<v8::String>());
 }
 
 void ScriptDebugServer::removeBreakpoint(const String& breakpointId)
 {
     v8::HandleScope scope(m_isolate);
     v8::Local<v8::Context> debuggerContext = v8::Debug::GetDebugContext();
@@ skipping 522 matching lines @@
 {
     return PassOwnPtr<ScriptSourceCode>();
 }
 
 String ScriptDebugServer::preprocessEventListener(LocalFrame*, const String& source, const String& url, const String& functionName)
 {
     return source;
 }
 
 } // namespace WebCore