Fixes retrieveSubModel in ConnectedAASManager

Fixes NullpointerException in retrieveSubModel when asked for a nonexistent Submodel

Signed-off-by: Maximilian Conradi <maximilian.conradi@iese.fraunhofer.de>
Change-Id: I3d3948d69e4239365c7b7e402d20578f9cb2514b
2 files changed