Compatibility fix for CraftBukkit and Spigot

• This update fixes a bug that was occurring on CraftBukkit and Spigot when trying to detect server shutdowns using the isStopping() method. This method was only available in Paper, which resulted in server shutdown detection not working.
• Debug has been added to improve bug finding, in case this doesn't work either
• Compatible with 1.20.2/3 (Or at least it compiled with spigot api 1.20.3 without additional errors)