EMSUSD-266 Fixed bad USD/UFE notifications

[deboisj]

Fixed bad notification translation. See comments in PR.
(also see https://forum.aousd.org/t/what-are-inert-prims/330)

Also fixed a thrown exception when object add fails for whatever reason.

[seando-adsk]

Suggested change

	// Note : Do nothing here with didRemoveInertPrim and didRemoveNonInertPrim.
	// Indeed, we can get these if prim specs are removed from some layers, but it
	// does not mean that the prim is not longer in the composed stage. If the prim
	// was actually gone, we would either get an invalid prim (in which case we
	// would not even get here, and would send a object destroyed" notif in the else
	// bellow), or we would fall into the "HasInfoChange : Active" case bellow. If
	// nothing else sends a notif in the loop (typically via the info change :
	// active) we do not want to send the fallback notif, so act as if a notif was
	// sent.
	// Note : Do nothing here with didRemoveInertPrim and didRemoveNonInertPrim.
	// Indeed, we can get these if prim specs are removed from some layers, but it
	// does not mean that the prim is no longer in the composed stage. If the prim
	// was actually gone, we would either get an invalid prim (in which case we
	// would not even get here, and would send a object destroyed" notif in the else
	// below), or we would fall into the "HasInfoChange : Active" case below. If
	// nothing else sends a notif in the loop (typically via the info change :
	// active) we do not want to send the fallback notif, so act as if a notif was
	// sent.

Minor typos. If you add only this commit (changing just the comment) then there is no need to re-run the preflight.