trade.lua error

[daretmavi]

Hi ,

I sometimes get this error if I try to trade with some NPC:

2021-03-03 23:39:10: ERROR[Main]: ServerError: AsyncErr: ServerThread::run Lua: Runtime error from mod 'advanced_npc' in callback on_playerReceiveFields(): /home/daret/.minetest/mods/advanced_npc/trade/trade.lua:184: attempt to index field 'price' (a nil value)
2021-03-03 23:39:10: ERROR[Main]: stack traceback:
2021-03-03 23:39:10: ERROR[Main]: 	/home/daret/.minetest/mods/advanced_npc/trade/trade.lua:184: in function 'show_trade_offer_formspec'
2021-03-03 23:39:10: ERROR[Main]: 	/home/daret/.minetest/mods/advanced_npc/trade/trade.lua:74: in function 'action'
2021-03-03 23:39:10: ERROR[Main]: 	/home/daret/.minetest/mods/advanced_npc/dialogue.lua:683: in function </home/daret/.minetest/mods/advanced_npc/dialogue.lua:619>
2021-03-03 23:39:10: ERROR[Main]: 	/usr/share/minetest/builtin/game/register.lua:422: in function </usr/share/minetest/builtin/game/register.lua:406>

You have to try it more times, but eventually after I clicker BUY I get this error.