Prevent unnecessary recursion when value is already expanded

[chasinglogic]

I had a similar change for StringSubber but it provided little to no perf gain so I have neglected to add it. I can make that change again however if it's decided these should work as similarly as possible.

Contributor Checklist:

• I have created a new test or updated the unit tests to cover the new/changed functionality.
• I have updated master/src/CHANGES.txt directory (and read the README.txt in that directory)
• I have updated the appropriate documentation