fix alias for treeroot

trunks/nodes.lua

@@ -365,5 +365,5 @@ for i in pairs(TRuNKS) do
 end
 end
 
-minetest.register_alias("trunks:treeroot", "default:air")
+minetest.register_alias("trunks:treeroot", "air")
 minetest.register_alias("trunks:pine_trunkroot", "trunks:pine_treeroot")