Merge remote-tracking branch 'origin/master' into andre/babe-skip-epochs

frame/babe/src/lib.rs

@@ -582,6 +582,12 @@ impl<T: Config> Pallet<T> {
 		// by the session module to be called before this.
 		debug_assert!(Self::initialized().is_some());
 
+		if authorities.is_empty() {
+			log::warn!(target: LOG_TARGET, "Ignoring empty epoch change.");
+
+			return
+		}
+
 		// Update epoch index.
 		//
 		// NOTE: we figure out the epoch index from the slot, which may not