if you create a pair and then delete your gateway it shows up as BTC/STR (undefined)
clarification added by iris:
if you create a pair and then remove the gateway using manage currencies, it shows up as BTC/STR (undefined)
PR https://github.com/stellar/stellar-client/pull/970 makes a lot of changes to this system. This bug might not be reproducible after it is merged. Check back after it is merged.
This is not reproducible anymore. I'm guessing that #970 fixed it.
Closing issue
@irisli I just reproduced this behavior.

When we revoke trust from a gateway it is completely removed form the wallet. Since you could still hold their credits, and therefore continue to trade, we should persist the gateway in the user's wallet after revoking trust.
Misunderstood, thought it was about deleting a pair.
This seems like something we need to discuss about. Should we keep traces of that gateway until all the credits are removed? Then we delete the gateway completely after the user doesn't have those credits anymore.
We will need the gateway info even after the credits are gone to properly show the trade history.