Possibility to prevent emitting faulthy messages

### Description

Hi all,

I received last night an issue for the svg-ui node, that reminded me of another drawback of the old V1 dashboard:

1. A message was injected into the node
2. One of the server-side validations in the `beforeEmit` detects a faulty input in that input message. So you want to ignore the message, but there was no way to prevent it from being emitted to the frontend. So you needed to add some extra info X to the message.
3. When the message arrived in the frontend, you had to ignore it when it contained the info X.

This workaround was provided a long time ago after a long discussion we had about this on Discourse. But it is a dirty workaround, which leads to messy code and useless traffic to the frontend...

And if you want to store the state on the server-side (as in my [drawing](https://github.com/flowforge/flowforge-nr-dashboard/issues/61#issuecomment-1684530029)), you simply want to ignore such messages: don't update the server-side state and as a result nothing is send to the frontend.

Perhaps this is already solved in the new dashboard, but just to make sure ;-)

Thanks!!

Bart

### Have you provided an initial effort estimate for this issue?

I am no FlowForge team member