Changes

Summary

1. Add fail_if_not_exists (#1524) (commit: 20e7499) (details)

Commit 20e7499beeaa1535bfd685d2fde73892237782b2 by noreply Add fail_if_not_exists (#1524) (commit: 20e7499)
	src/main/java/net/dv8tion/jda/api/entities/Message.java (diff)
	src/main/java/net/dv8tion/jda/api/requests/restaction/MessageAction.java (diff)
	src/main/java/net/dv8tion/jda/internal/requests/restaction/MessageActionImpl.java (diff)