From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sat, 11 Apr 2020 21:38:59 -0400
Subject: [PATCH] Disable Sync Events firing Async errors during shutdown

This is how it use to behave on Paper, and this is totally destroying
the ability to try to shut the server down gracefully during the
shutdown process as events firing on the watchdog thread are throwing
errors.

This isn't an issue on Spigot

diff --git a/src/main/java/org/bukkit/plugin/SimplePluginManager.java b/src/main/java/org/bukkit/plugin/SimplePluginManager.java
index 8355f9f0eb1b554bf6cfd3883afd2bdd2bf8c357..4931bc86d44cd697d458d6e365c3b8030ea8285d 100644
--- a/src/main/java/org/bukkit/plugin/SimplePluginManager.java
+++ b/src/main/java/org/bukkit/plugin/SimplePluginManager.java
@@ -591,7 +591,7 @@ public final class SimplePluginManager implements PluginManager {
         // Paper - replace callEvent by merging to below method
         if (event.isAsynchronous() && server.isPrimaryThread()) {
             throw new IllegalStateException(event.getEventName() + " may only be triggered asynchronously.");
-        } else if (!event.isAsynchronous() && !server.isPrimaryThread()) {
+        } else if (!event.isAsynchronous() && !server.isPrimaryThread() && !server.isStopping() ) {
             throw new IllegalStateException(event.getEventName() + " may only be triggered synchronously.");
         }