Spring RTS Engine

Does anyone know how to fix this and why it occurs? 0] Loading LuaUI [ 0] Using LUAUI_DIRNAME = LuaUI/ [ 0] Reloaded ctrlpanel with: LuaUI/ctrlpanel.txt [ 0] Lua LoadCode pcall error = 2, luaui.lua, error = 2, LuaUI/widgets.lua, [string "LuaUI/widgets.lua"]:33: attempt to concatenate globa...