Disallow player movement while talking with traders

[martypenner]

This was the case in a far earlier version of the game, but somewhere, somehow, a regression snuck in.

[martypenner]

I should add that the call to check if the "confirm" button has been pressed to initiate the dialog is being called twice. Strange.

[martypenner]

No guard clause was in effect to check whether the player was near to the current trader being checked (for distance to the player), so the code was being called once for every trader spawned. Since we originally only had 1 trader in-game, there was no issue.