Fix Tile::getTopLookThing()

Fixing an issue which returned splash items instead of real usable items.
In case a blood splash is inside an open door, you are unable to close it. This patch will ignore splash items and return the real usable item correctly.

~~~~Lord Hepipud~~~~
Merge pull request #484 from LordHepipud/patch-3

Fix Tile::getTopUseThing()