invisible command meta tweak and player online check

plugin/src/main/java/com/denizenscript/denizen/scripts/commands/entity/InvisibleCommand.java

@@ -40,13 +40,16 @@ public InvisibleCommand() {
     // @Group entity
     //
     // @Description
-    // Makes the specified entity invisible, defaults to the linked player/NPC if one wasn't specified.
+    // Makes the specified entity invisible (equivalent to an invisibility potion), defaults to the linked player/NPC if one wasn't specified.
     // If an NPC was specified, the 'invisible' trait is applied.
     //
     // Optionally specify 'for:' with a list of players to fake the entity's visibility state for these players.
     // When using the 'toggle' state with the 'for:' argument, the visibility state will be toggled for each player separately.
-    // Note that using the 'for:' argument won't apply the 'invisible' trait to NPCs.
     // If unspecified, will be set globally.
+    // 'For' players remain tracked even when offline/reconnecting, but are forgotten after server restart.
+    // Note that using the 'for:' argument won't apply the 'invisible' trait to NPCs.
+    //
+    // When not using 'for', the effect is global / on the real entity, which will persist in that entity's data until changed.
     //
     // To reset an entity's fake visibility use the 'reset' state.
     // A reset is global by default, use the 'for:' argument to reset specific players.
@@ -121,7 +124,7 @@ public static void setInvisibleForPlayer(EntityTag target, PlayerTag player, boo
         HashMap<UUID, Boolean> playerMap = invisibleEntities.computeIfAbsent(target.getUUID(), k -> new HashMap<>());
         wasModified = !playerMap.containsKey(player.getUUID()) || playerMap.get(player.getUUID()) != invisible || wasModified;
         playerMap.put(player.getUUID(), invisible);
-        if (wasModified) {
+        if (wasModified && player.isOnline()) {
             NMSHandler.packetHelper.sendEntityMetadataFlagsUpdate(player.getPlayerEntity(), target.getBukkitEntity());
         }
     }