Fix headless build

src/override/RemoteWindow.cpp

@@ -140,6 +140,7 @@ struct Window::Internal
 	std::map<std::string, std::shared_ptr<Image>> imageCache;
 
 	bool fbDirtyOnSubpixelChange = true;
+	int fbCount = 0;
 
 #ifdef WITH_MESA
 	void run() override {
@@ -359,6 +360,7 @@ void Window::step() {
 	double lastFrameTime = internal->frameTime;
 	internal->frameTime = frameTime;
 	internal->lastFrameDuration = frameTime - lastFrameTime;
+	internal->fbCount = 0;
 	// DEBUG("%.2lf Hz", 1.0 / internal->lastFrameDuration);
 
 	// Make event handlers and step() have a clean NanoVG context
@@ -507,6 +509,11 @@ bool& Window::fbDirtyOnSubpixelChange() {
 }
 
 
+int& Window::fbCount() {
+	return internal->fbCount;
+}
+
+
 } // namespace window
 } // namespace rack