Improper trade causes negative resources

[Former user]

I saw a trade in the scan tab which was 500 power for 9 batteries. I only had 3 batteries, but I clicked on the trade and ended up with -6 batteries, which gives me -50 power storage. I can no longer have any power.

[Kev Bourque]

Fixed this in b38a. Trades no longer are able to be done if you can't afford them.

On the off-chance the player can still get their batteries into the negative, it will no longer put the maximum power into the negative.