Fix "Array to string conversion" error in SpecialVipsTest.php

> PHP Notice: Array to string conversion
> from line 362 of /srv/mediawiki/php-1.33.0-wmf.2
> /extensions/VipsScaler/SpecialVipsTest.php

Change-Id: Id9f82afdc20722ba138e3e69b885c3896971ac25
1 file changed