Fix mailbox error (#52)

`tiles` is not a required field. Indexing it may fail.

Fix #51

diff --git a/mailbox.lua b/mailbox.lua
index 1985eea888c06fbaaa2f87a44c35a90a35d9a862..f538ab61336b72856d61db0f21a009cf5e9b7a46 100644 (file)
--- a/mailbox.lua
+++ b/mailbox.lua
@@ -8,7 +8,12 @@ local function img_col(stack)
        if def.inventory_image ~= "" then
                return def.inventory_image:match("(.*)%.png")..".png"
        end
-       return def.tiles[1]:match("(.*)%.png")..".png"
+
+       if def.tiles and def.tiles[1] then
+               return def.tiles[1]:match("(.*)%.png")..".png"
+       end
+
+       return ""
 end
 
 function mailbox:formspec(pos, owner, num)