F5 polling fails for new virtual servers

Poller doesn't seem to be able to process virtual servers from F5 anymore.
Don't know when it started - updated from 11524 to 11565 but issues persists.

Error when poller is executed manually:

o F5-BIGIP-LOCAL-MIB F5-BIGIP-LOCAL-MIB
o Collecting F5-BIGIP-LOCAL-MIB Virtual Servers
PHP Fatal error: Uncaught TypeError: array_merge(): Argument #1 must be of type array, null given in /srv/observium/includes/polling/loadbalancer/f5-bigip-local-mib.inc.php:109
Stack trace:
#0 /srv/observium/includes/polling/loadbalancer/f5-bigip-local-mib.inc.php(109): array_merge()
#1 /srv/observium/includes/include-dir-mib.inc.php(46): include('...')
#2 /srv/observium/includes/polling/loadbalancer.inc.php(15): include('...')
#3 /srv/observium/includes/polling/functions.inc.php(334): include('...')
#4 /srv/observium/poller.php(171): poll_device()
#5

thrown in /srv/observium/includes/polling/loadbalancer/f5-bigip-local-mib.inc.php on line 109