Calling getfields for 'supannAccount' triggers JSON encoding error

Description

Calling getFields for tab 'supannAccount' using the API returns nothing

Distribution Name and Version

Whatever runs demo.fusiondirectory.org.

FusionDirectory Version

1.2

Plugin with the defect

Web Service

PHP version used

Whatever runs demo.fusiondirectory.org.

Origin of php packages

Whatever runs demo.fusiondirectory.org.

Steps to Reproduce

1. Use method getfields to get fields for the user tab 'supannAccount': {'params': ['ks66p6sfpgdi3n3q87qqnfp034', 'USER', None, 'supannAccount'], 'method': 'getfields', 'id': '123'}
2. Observe no data being returned by FD.

Expected behavior:

To get the fields in the user tab 'supannAccount'.

Actual behavior:

FD returns no data.

Reproduces how often:

100%