in fields with 'multiSelect: true', we get an array as value instead
of a string, but a check of !![] results in true (since an array
is an object), so we have to explicitely check for arraylength
in 'setValue' (for correctly showing the trigger) and in the
load handler (to not set an empty field wrongfully to invalid)
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>