[BUGFIX] Reset SYS/exceptionalErrors in live preset

Resolves: #76901
Releases: master, 7.6, 6.2
Change-Id: I50167e4d64ef9cda8d39e9f2e03fc08e3de646b1
Reviewed-on: https://review.typo3.org/48763


Tested-by: Bamboo TYPO3com <info@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>