[BUGFIX] Added handling for array in findOneByXXX result

If query findOneByXXX is configured to return an array, the first array
element is returned (instead of calling ->getFirst() on a non object).

Fixes: #46035
Releases: 6.1, 6.0, 4.7, 1.3
Change-Id: I2c9d3083ce0eaebd2929ce9f50ec2a7cc36fe222
Reviewed-on: https://review.typo3.org/19855
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn