[Tilesathome] Fixed close-areas

[Frederik Ramm]

Hi,

    User Alfons has sent me a fix for a bug in close-areas that would 
cause rendering breakage for some water tiles like

http://server.tah.openstreetmap.org/Browse/?layer=tile&z=12&x=3539&y=2061
http://server.tah.openstreetmap.org/Browse/?layer=tile&z=12&x=905&y=1328

I checked it in and I hope it works.

Thanks Alfons for looking into this.

Bye
Frederik