DrawGradient( const PolyPolygon&... etc) gets graphics instance too early

The OutputDevice::DrawGradient function that takes a PolyPolygon checks
for a graphics instance far too early. It then checks it again when it
actually needs it, but we really only need to get it once.

Change-Id: I2426dfe2e5c03f0e8e3939b53b16c99afe637812

vcl/source/gdi/outdev4.cxx

@@ -812,10 +812,6 @@ void OutputDevice::DrawGradient( const PolyPolygon& rPolyPoly,
     if( mbOutputClipped )
         return;
 
-    if( !mpGraphics )
-        if( !ImplGetGraphics() )
-            return;
-
     if( rPolyPoly.Count() && rPolyPoly[ 0 ].GetSize() )
     {
         if ( mnDrawMode & ( DRAWMODE_BLACKGRADIENT | DRAWMODE_WHITEGRADIENT | DRAWMODE_SETTINGSGRADIENT) )