Avoid throwing an error if private key is missing unless .send() is executed

[marekyggdrasil]

Hello everyone. I am working on a contribution to SnarkyJS and I am opening this thread just to have a corresponding issue to my pull request.

The problem I discovered while working on https://github.com/sqrt-xx/mina-ui-deployment, particularly, I could not sign the zkApp deployment transaction using AURO. There is nothing wrong with AURO signing capabilities. The problem originates from SnarkyJS as it will raise an exception if signer private key is missing during the transaction building when account creation fee is included.

The related discussion thread is: https://discord.com/channels/484437221055922177/1109079490111479848

[marekyggdrasil]

Many thanks for guidance and letting me help fixing this!