Add an IfError Function to the OpCon Expression API

I would like the Expression API to be updated to include an "IfError" function.

Ideally, this would have 3 parameters:

1. The Expression to be evaluated
2. What to return if the expression errored
3. What to return if the expression didn't error (by default this would return the results of the expression)

Here's the use case for this scenario:

Through Self-Service, we have a button that adds a job to a schedule. I want this button to be disabled while the job that it would add is currently running (so that it can't be added again until it's finished). What I would like to do, is use an expression in the Disable Rule field to determine if the job is currently running. Something like:

[[JI.$JOB STATUS.CURRENT.Temp.Test Job]]== "Running"

However, if the job doesn't actually exist, the expression evaluator errors out, and this disables the button. It appears the button will always be disabled unless the expression equals "False". Thereby, errors in the expression also disable the but