Yeah, this tidbit got lost in the realm of SR5. It is weird, Shadowrun is so crunchy, but sometimes it seems that very important chunk is forgotten.
In my game, I've ruled out to to reimplement the 3ed rule. If the mage is put in overflow while fighting in the astral, connection is broken, he is thrown back into his body, dying - and if someone is around to save him he awakes with one less magic point. It makes astral battle and travel more dangerous, which I think is a good idea has it can easily be (mis)used by PCs to go around difficulties. (but, again, IMHO, and I tend to be more black trench coat than pink mohawk)
BTW, it would be nice to have an official errata (Just realised I did not check the Missions FAQ, maybe this is cover there ?), but certainly not a big deal....