API Inventory error

No data return from API inventory module.
Appears to be an issue in the code:
Warning: array_pop() expects parameter 1 to be array, null given in /opt/observium/libs/ref.inc.php on line 779

see debug below.
----------------------------------------------------
DEBUG Returned User authentification:

Warning: array_pop() expects parameter 1 to be array, null given in /opt/observium/libs/ref.inc.php on line 779

array(2
id => 142309
level => 10
)
DEBUG Returned Error Code:

Warning: array_pop() expects parameter 1 to be array, null given in /opt/observium/libs/ref.inc.php on line 779
array(1
success => array(2)
)
DEBUG Loading module:

Warning: array_pop() expects parameter 1 to be array, null given in /opt/observium/libs/ref.inc.php on line 779
array(2
module => inventory
file => includes/api/module.inventory.inc.php
)
DEBUG Returned device permitted:

Warning: array_pop() expects parameter 1 to be array, null given in /opt/observium/libs/ref.inc.php on line 779
true
DEBUG Returned JSON data:

Warning: array_pop() expects parameter 1 to be array, null given in /opt/observium/libs/ref.inc.php on line 779
array(2
login => array(1)
data => array()
)
DEBUG Returned Encrypted JSON data:

Warning: array_pop() expects parameter 1 to be array, null given in /opt/observium/libs/ref.inc.php on line 779
{"login":{"success":{"code":"101","msg":"User authentification succeeded"}},"data":[]}
----------------------------------------------------