When the level.dat has incorrect data, the end dragon fight can completely fail to start, causing the end to have no exit portal (activated or not) and no end dragon. The crystals generate properly however.

Linked is a broken world download, a broken level.dat, a working level.dat, and screenshots of level.dat in both cases.

The end was *NOT VISITED* prior to 15w44b however the world was created in earlier snapshots