So last night Blue Wallet built a multi signature transaction for me with NO change address.

Seedsigner fortunately pointed this out to me in its interface. So I did not broadcast this transaction.

Is this a bug in Blue Wallet (Android) or some kind of mistake on my behalf?

This was about a $10 transaction with a wallet that contained WAY more than that.

If I had broadcast this transaction I would have lost it all right?

How can I ensure that this doesn't happen again?