Add a check for empty handle in V8Proxy::GetSourceLineNumber()...

webkit/port/bindings/v8/v8_proxy.cpp

 // Copyright (c) 2008, 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 3456 matching lines @@
     if (utility_context.IsEmpty()) {
         return 0;
     }
     v8::Context::Scope context_scope(utility_context);
     v8::Handle<v8::Function> frame_source_line;
     frame_source_line = v8::Local<v8::Function>::Cast(
         utility_context->Global()->Get(v8::String::New("frame_source_line")));
     if (frame_source_line.IsEmpty()) {
         return 0;
     }
-    return v8::Debug::Call(frame_source_line)->Int32Value();
+    v8::Handle<v8::Value> result = v8::Debug::Call(frame_source_line);
+    if (result.IsEmpty()) {
+        return 0;
+    }
+    return result->Int32Value();
 }
 
 
 String V8Proxy::GetSourceName() {
     v8::HandleScope scope;
     v8::Handle<v8::Context> utility_context = GetUtilityContext();
     if (utility_context.IsEmpty()) {
         return String();
     }
     v8::Context::Scope context_scope(utility_context);
     v8::Handle<v8::Function> frame_source_name;
     frame_source_name = v8::Local<v8::Function>::Cast(
         utility_context->Global()->Get(v8::String::New("frame_source_name")));
     if (frame_source_name.IsEmpty()) {
         return String();
     }
     return ToWebCoreString(v8::Debug::Call(frame_source_name));
 }
 
 void V8Proxy::RegisterExtension(v8::Extension* extension) {
     v8::RegisterExtension(extension);
     m_extensions.push_back(extension);
 }
 
 }  // namespace WebCore