refactors, code style fixes, rpeventing events from firing when not needed

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

@@ -45,4 +45,10 @@ public class PlayerLeaveCombatEvent extends Event implements Cancellable {
     public HandlerList getHandlers() {
         return HANDLERS;
     }
+
+    @NotNull
+    public static HandlerList getHandlerList() {
+        return HANDLERS;
+    }
+
 }