There are legitimate cases when a Map-Request does not contain a Source-EID, such as the standalone 'lig' utility, which shouldn't really be considered a subscriber to a mapping when it is run from a standalone host (as opposed to an xTR with a mapping cache). In this case it doesn't make sense to store the originator as a subscriber, and send SMRs on mapping changes, since there is no process listening for these control messages.

The current code does store subscribers with no Source-EID, and attempts to send an SMR, but this results in an exception, since the Source-EID is now required (it wasn't previously).

The correct behavior should be not to store subscribers without a Source-EID at all.