[BUGFIX] Prevent submitting LiveSearch form

Hitting enter in the LiveSearch form results in a reload
of the TYPO3 backend. Prevent the submit action with JavaScript.

Resolves: #71481
Releases: master
Change-Id: Ie6fd69d481501d5380cff11fce24dc58ea745e81
Reviewed-on: https://review.typo3.org/44692


Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Tested-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Reviewed-by: Michael Oehlhof <typo3@oehlhof.de>
Tested-by: Michael Oehlhof <typo3@oehlhof.de>
Reviewed-by: Josef Glatz <josef.glatz@typo3.org>
Tested-by: Josef Glatz <josef.glatz@typo3.org>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Tested-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>