openhab-core: Mixing gui and files for semantic model does not work

Defining the semantic model partly in the gui and partly in item-files breaks after restarting openhab.

Steps to reproduce:

• Add a location group “test” in the gui.
• Add a point in an item-file: Number test_item "Test Item" <temperature> (test) ["Measurement", "Temperature"]

At first the Test Item is shown as child in the semantic model but after a restart of openhab it is moved to the root level. See also here