[DevTools] fixed console.count with empty stack

third_party/WebKit/Source/platform/v8_inspector/V8Console.cpp

Index: third_party/WebKit/Source/platform/v8_inspector/V8Console.cpp
diff --git a/third_party/WebKit/Source/platform/v8_inspector/V8Console.cpp b/third_party/WebKit/Source/platform/v8_inspector/V8Console.cpp
index fdcd662b0fceac5f71cb90616b3c414d500617e4..a6998d6ebeff2c949e9fd2b503ab55d47a64f39f 100644
--- a/third_party/WebKit/Source/platform/v8_inspector/V8Console.cpp
+++ b/third_party/WebKit/Source/platform/v8_inspector/V8Console.cpp
@@ -357,7 +357,7 @@ void V8Console::countCallback(const v8::FunctionCallbackInfo<v8::Value>& info)
     String16 identifier;
     if (title.isEmpty()) {
         std::unique_ptr<V8StackTraceImpl> stackTrace = V8StackTraceImpl::capture(nullptr, 0, 1);
-        if (stackTrace)
+        if (stackTrace && !stackTrace->isEmpty())
             identifier = stackTrace->topSourceURL() + ":" + String16::fromInteger(stackTrace->topLineNumber());
     } else {
         identifier = title + "@";