Clerics in a previous edition did not need their divine powers to be granted by gods. In 5th edition, this seems to have changed. The introduction for clerics in the PHB says:

Divine magic, as the name suggests, is the power of the gods, flowing from them into the world. Clerics are conduits for that power, manifesting it as miraculous effects. The gods don’t grant this power to everyone who seeks it, but only to those chosen to fulfill a high calling.

However, I would like to handle a strange case in which clerics still exist, but the gods they serve are dead and hence unable to provide divine magic anymore. And while I can simply make up a reason why this is, I'd like to know: is there any official support for clerics wielding divine magic despite the absence/death of their gods in this edition?