coverity#708657 Uninitialized pointer field

Change-Id: Ief35e66ef2e1bcad39f7ff70fd39e91973a4dc69

vcl/generic/print/genpspgraphics.cxx

@@ -145,6 +145,7 @@ SalPrinterBmp::SalPrinterBmp (BitmapBuffer* pBuffer) :
 
         default:
             OSL_FAIL("Error: SalPrinterBmp::SalPrinterBmp() unknown bitmap format");
+            mpFncGetPixel = NULL;
         break;
     }
 }