Target will shows "Incompatible Target" if there is a blank computer object in the computer list. If you remove the blank objects by double-clicking them the target goes back to normal.
ITMS 8.5 RU2 or later
Query used to find the GUIDs:
select distinct rtmc.ResourceGuid
from TargetFilterResource rtmc
left join vRM_Resource_Item c on c.Guid = rtmc.ResourceGuid left join Item i on i.Guid = rtmc.TargetFilterGuid join TargetFilter tf on tf.Guid = rtmc.TargetFilterGuid where c.Guid is null
Query used to delete the GUIDs:
delete rtmc
from TargetFilterResource rtmc
left join vRM_Resource_Item c on c.Guid = rtmc.ResourceGuid left join Item i on i.Guid = rtmc.TargetFilterGuid join TargetFilter tf on tf.Guid = rtmc.TargetFilterGuid where c.Guid is null