Well thank you. I always used to think that it was built in. Didn't know it was just the wallets preventing from creating a transaction when there was an unconfirmed one.
So if it turns out to be a double spend, then the whole transaction would disappear i suppose ?
Yes. If the first transaction is invalidated by a double spend which confirms, then any transaction which spent from it is also invalidated. This can also happen if the first unconfirmed transaction pays too low of a fee and is "forgotten" by the network. The network will "forget" the second transaction too since they don't "remember" the first one. So if it turns out to be a double spend, then the whole transaction would disappear i suppose ?
