Strictly speaking, this check is only valid for `PRODUCER`s (i.e., when `wells.type[w] == PRODUCER`), at least using the current edition of `class WellsManager`.  This is, of course, a problem of the original code rather than the change-set being introduced in PR #454.  On the other hand, since you're in the area anyway, maybe you could fix that problem too?  That said, a future edition of the `WellsManager` could potentially impose other invariants on the phase distribution of `INJECTOR`s so I'm not sure how pressing the issue really is.

Commit 6a31f54 contains a few additional comments.