[BUG] /give and /trade fail silently when the giver has nothing in their inventory that can be given/traded

[rivques]

No description provided.

[rivques]

This occurs because Slack expects there to be something to put in the dropdown to select which item you want, and then gets mad when there isn't (e.g. if all your items are nontradeable, or in crafting/trades, or smth). This is exacerbated by #21 , because there's another reason to disqualify items from being able to be traded. However, this is likely a small issue in practice because onboarding should ensure everybody has some items.