Duplicate runs of the "rate" script result in duplicate entries

[theomega]

If you (accidentially) run the "rates" script twice, you end up with two times the "magic number" subtracted/added. The transact_rate_balance method should check if there is already an entry for today and if yes update that one instead of creating a new one.

[arecker]

Ah good catch. I'll be sure to add a check.