We can't have more than one NOTE_SUBTYPE in the same notifier.
This is a partial revert of: cd4d5dcb46. In particular to the part concerning
"Also fixed a missing notifier of the object instancing operator".
Not only this was mixed with the original reason for the commit for no reason,
but it actually introduced a bug. Bad, bad developers ;)
Note: Although this commit is not needed for master, blender2.8 requires it for
the forementioned bug report.
8e341633e9