Blind fix for !CG

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@53960 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/mac/carbon/dcscreen.cpp

@@ -79,6 +79,7 @@ wxScreenDC::~wxScreenDC()
 
 wxBitmap wxScreenDC::DoGetAsBitmap(const wxRect *subrect) const
 {
+#if wxMAC_USE_CORE_GRAPHICS
     CGRect srcRect = CGRectMake(0, 0, m_width, m_height);
     if (subrect)
     {
@@ -109,4 +110,7 @@ wxBitmap wxScreenDC::DoGetAsBitmap(const wxRect *subrect) const
     CGContextRestoreGState(context);
 
     return bmp;
+#else
+    return wxNullBitmap;
+#endif    
 }