skip overlay processing when no overlay is specified

src/main.cpp

@@ -138,9 +138,14 @@ int main(int argc, char *argv[])
     std::cout << "Rotation Time: " << rotationSeconds << std::endl;
     std::cout << "Overlay input: " << overlay << std::endl;
   }
+
   Overlay o(overlay);
   o.setDebugMode(debugMode);
+  if (!overlay.empty())
+  {
     w.setOverlay(&o);
+  }
+
   w.setAspect(aspect);
   w.setDebugMode(debugMode);
   w.setFitAspectAxisToWindow(fitAspectAxisToWindow);

src/mainwindow.h

@@ -39,7 +39,7 @@ private:
     bool debugMode = false;
     bool fitAspectAxisToWindow = false;
 
-    Overlay* overlay;
+    Overlay* overlay = NULL;
 
     void drawText(QPixmap& image, int margin, int fontsize, QString text, int alignment);