[BUGFIX] Simulate time in TYPO3 admin panel broken

* Test typeof TBE_EDITOR == "undefined" in jsfunc.evalfield
* Thanks to Stefan Neufeind/Markus Klein for adding the Unittest

Resolves: #55093
Releases: 6.2, 6.1, 6.0
Change-Id: I2cc8a5ca3dd6251f89618d3615c1457938ff135e
Reviewed-on: https://review.typo3.org/26895
Reviewed-by: Markus Klein
Tested-by: Markus Klein
Reviewed-by: Henrik Ziegenhain
Tested-by: Henrik Ziegenhain
Reviewed-by: Wouter Wolters
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind