Check form is valid in update path callback

https://app.getsentry.com/gostellarorg/stellar-client/group/35926009/
https://app.getsentry.com/gostellarorg/stellar-client/group/35927479/

this doesn't fix the core issue but it gets rid of the many sentry errors we're seeing. let's merge this to get rid of those errors and priorityize the refacotr