[1.9.0 FIXED] Portal consumes mana/crystal in forest but does not remove tree tiles

[sasbot]

In the forest level, tree tiles remain unaffected by the portal spell despite them being valid targets and it consuming mana and a crystal as with a normal successful cast.

[zefz]

Ah this is because trees are not walls and the spell should therefore work at all.

I've fixed it so that the spell does not use mana nor consume crystal when cast on a tree.