[Extensions] Don't pass empty value to V8Converter in OnJSInjectionCompleted

extensions/renderer/script_injection.cc

Index: extensions/renderer/script_injection.cc
diff --git a/extensions/renderer/script_injection.cc b/extensions/renderer/script_injection.cc
index 0a440f9ce8367023344adc42818c75854839501d..5165ed1bbd7acec0150afca005261257b14ac37b 100644
--- a/extensions/renderer/script_injection.cc
+++ b/extensions/renderer/script_injection.cc
@@ -305,7 +305,7 @@ void ScriptInjection::OnJsInjectionCompleted(
   bool expects_results = injector_->ExpectsResults();
   if (expects_results) {
     scoped_ptr<base::Value> result;
-    if (!results.isEmpty()) {
+    if (!results.isEmpty() && !results[0].IsEmpty()) {
       // Right now, we only support returning single results (per frame).
       scoped_ptr<content::V8ValueConverter> v8_converter(
           content::V8ValueConverter::create());