Initialize wxMemoryDC with a default font

src/msw/dcmemory.cpp

@@ -70,6 +70,7 @@ void wxMemoryDCImpl::Init()
     {
         SetBrush(*wxWHITE_BRUSH);
         SetPen(*wxBLACK_PEN);
+        SetFont(*wxNORMAL_FONT);
 
         // the background mode is only used for text background and is set in
         // DrawText() to OPAQUE as required, otherwise always TRANSPARENT