Less annoying nanovg error logs when it fails to initialize

dgl/src/NanoVG.cpp

@@ -280,12 +280,12 @@ NanoVG::~NanoVG()
 
 void NanoVG::beginFrame(const uint width, const uint height, const float scaleFactor)
 {
-    if (fContext == nullptr) return;
     DISTRHO_SAFE_ASSERT_RETURN(scaleFactor > 0.0f,);
     DISTRHO_SAFE_ASSERT_RETURN(! fInFrame,);
     fInFrame = true;
 
-    nvgBeginFrame(fContext, static_cast<int>(width), static_cast<int>(height), scaleFactor);
+    if (fContext != nullptr)
+        nvgBeginFrame(fContext, static_cast<int>(width), static_cast<int>(height), scaleFactor);
 }
 
 void NanoVG::beginFrame(Widget* const widget)

tests/NanoSubWidgets.cpp

@@ -132,8 +132,11 @@ public:
     {
         const uint targetWidth = 400;
         const uint targetHeight = 400;
+        const double scaleFactor = getScaleFactor();
 
-        setSize(targetWidth, targetHeight);
+        setGeometryConstraints(targetWidth, targetHeight, true);
+        setResizable(true);
+        setSize(targetWidth * scaleFactor, targetHeight * scaleFactor);
         setTitle("NanoVG SubWidgets test");
     }