[BUGFIX] #5187 mb_strlen(): Unknown encoding in tx_realty_Model_RealtyObjectTest

Change-Id: I715fb171d1e814b134c14d63e307ac14d0f50611
Reviewed-on: http://review.typo3.org/34891
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>