lazmapviewer: Fix mismatch of checked items for distance calculation after r6879 (https://forum.lazarus.freepascal.org/index.php/topic,12674.msg319432.html, patch by sstvmaster).

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@6883 8e941d3f-bd1b-0410-a28a-d453659cc2b4

components/lazmapviewer/source/mvmapviewer.pas

@@ -517,6 +517,7 @@ begin
     {$IFDEF USE_LAZINTFIMAGE}
     bmp := TBitmap.Create;
     try
+      bmp.PixelFormat := pf32Bit;
       bmp.SetSize(Buffer.Width, Buffer.Height);
       bmp.LoadFromIntfImage(Buffer);
       Canvas.Draw(0, 0, bmp);