[BUGFIX] t3editor: Harden some checks for TS parsing

Resolves: #88262
Resolves: #85346
Releases: master, 9.5
Change-Id: Ia72ef1b670841d90ec0251c99b7f4d3dc1e7770a
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60900


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Riccardo De Contardi <erredeco@gmail.com>
Tested-by: Sven Juergens <typo3@blue-side.de>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>