[BUGFIX] Trim input into xml2array

Preciding whitespace in the xml input string causes xml2array()
to fail with an error message. This whitespace is often
introduced by formatting code via IDE, so blaming the developer
only helps so far. Inserting a trim() before the input is processed
mitigates the problem.

Resolves: #78752
Releases: master, 7.6
Change-Id: I3b9d3c81b64d502e7cefef80e72bef3a1bd9b3da
Reviewed-on: https://review.typo3.org/50716


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Łukasz Uznański <l.uznanski@macopedia.pl>
Tested-by: Łukasz Uznański <l.uznanski@macopedia.pl>
Reviewed-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>