Possible fix for NPE being thrown when sending resource-packs in the configuration stage (#181)

(cherry picked from commit 62c42c0)

Author: Grabsky

src/main/java/de/oliver/fancyholograms/listeners/PlayerListener.java

@@ -72,6 +72,10 @@ public void onWorldChange(@NotNull final PlayerChangedWorldEvent event) {
 
     @EventHandler(priority = EventPriority.MONITOR)
     public void onResourcePackStatus(@NotNull final PlayerResourcePackStatusEvent event) {
+        // Skipping event calls before player has fully loaded to the server.
+        // This should fix NPE due to vanillaPlayer.connection being null when sending resource-packs in the configuration stage.
+        if (!event.getPlayer().isOnline())
+            return;
         final UUID playerUniqueId = event.getPlayer().getUniqueId();
         final UUID packUniqueId = getResourcePackID(event);
         // Adding accepted resource-pack to the list of currently loading resource-packs for that player.