For numeric input, an expression that couldn't evaluate was printing an error to the stdout (see T84417).

With this patch, the text "Invalid" is replaced with the exception message (without the full stack trace).

A down side for this patch is the exception text isn't clearly differentiated with the other fields, changing this would require number input not to rely on plain text to draw the number editing field.

Without this, there is no way for users to know what the error is while transforming (unless they have a terminal window open).

It is possible to look in the info window, but that's only possible after the numeric input has closed.