only fire PlayerEnterCombatEvent if there are registered listeners for it

src/main/java/me/youhavetrouble/preventstabby/api/event/PlayerEnterCombatEvent.java

@@ -45,4 +45,9 @@ public class PlayerEnterCombatEvent extends Event implements Cancellable {
     public HandlerList getHandlers() {
         return HANDLERS;
     }
+
+    @NotNull
+    public static HandlerList getHandlerList() {
+        return HANDLERS;
+    }
 }

src/main/java/me/youhavetrouble/preventstabby/util/CombatTimer.java

@@ -17,8 +17,11 @@ public class CombatTimer {
             if (player == null || !player.isOnline()) return;
             PlayerEnterCombatEvent playerEnterCombatEvent = new PlayerEnterCombatEvent(player);
             Bukkit.getScheduler().runTask(PreventStabby.getPlugin(), () -> {
+                if (PlayerEnterCombatEvent.getHandlerList().getRegisteredListeners().length > 0) {
                     Bukkit.getPluginManager().callEvent(playerEnterCombatEvent);
                     if (playerEnterCombatEvent.isCancelled()) return;
+                }
+
                 PreventStabby.getPlugin().getPlayerManager().refreshPlayersCombatTime(uuid);
 
                 if (combattime <= 0) {