SPIGOT-4714: Broadcasts can no longer be done from secondary threads

src/main/java/org/bukkit/craftbukkit/CraftServer.java

@@ -1263,7 +1263,7 @@ public final class CraftServer implements Server {
             }
         }
 
-        BroadcastMessageEvent broadcastMessageEvent = new BroadcastMessageEvent(message, recipients);
+        BroadcastMessageEvent broadcastMessageEvent = new BroadcastMessageEvent(!Bukkit.isPrimaryThread(), message, recipients);
         getPluginManager().callEvent(broadcastMessageEvent);
 
         if (broadcastMessageEvent.isCancelled()) {