Assume that nDPI should never be zero in ImplLogicToPixel

...(same as is already done in ImplPixelToLogic), and that
eacbead4 "vcl: handle nDPI == 0 in
ImplPixelToLogic()" was a misguided attempt at fixing symptoms of the problem
fixed with 670100fc "Remove FastLoader
optimization."

Change-Id: Ia42c6c7c7026f3a0b71e79938b33c140fec0afa6

vcl/source/outdev/map.cxx

@@ -400,9 +400,10 @@ static long ImplLogicToPixel( long n, long nDPI, long nMapNum, long nMapDenom,
 static long ImplPixelToLogic( long n, long nDPI, long nMapNum, long nMapDenom,
                               long nThres )
 {
+    assert(nDPI > 0);
     // To "use" it...
    (void) nThres;
-   if (nMapNum == 0 || nDPI == 0)
+   if (nMapNum == 0)
    {
        return 0;
    }