Fix get_decoration handling of tables.

deco.lua

@@ -376,7 +376,11 @@ local function get_decoration(biome_name)
     if not deco.biomes or deco.biomes[biome_name] then
       if deco.deco_type == "simple" then
         if deco.fill_ratio and math.random(1000) - 1 < deco.fill_ratio * 1000 then
-          return deco.decoration
+          if type(deco.decoration) == 'string' then
+            return deco.decoration
+          elseif type(deco.decoration) == 'table' then
+            return deco.decoration[math.random(#deco.decoration)]
+          end
         end
       end
     end