vcl: Update current context before executing scale operation

Change-Id: I332c954259bdc7e34718449023f5aa82323987cc

vcl/opengl/scale.cxx

@@ -252,6 +252,8 @@ bool OpenGLSalBitmap::ImplScale( const double& rScaleX, const double& rScaleY, s
 {
     SAL_INFO( "vcl.opengl", "::ImplScale" );
 
+    makeCurrent();
+
     if( nScaleFlag == BMP_SCALE_FAST )
     {
         return ImplScaleFilter( rScaleX, rScaleY, GL_NEAREST );