Prevent NPE in getPlayerLocale for offline players (#6435)

I hope this message finds you well. This pull requests prevents an NPE
in getPlayerLocale for offline players.

Co-authored-by: JRoy <10731363+JRoy@users.noreply.github.com>

Author: kennytv

Essentials/src/main/java/com/earth2me/essentials/User.java

@@ -841,7 +841,7 @@ public void checkActivity() {
                 && !isAuthorized("essentials.afk.kickexempt")) {
             lastActivity = 0;
             final double kickTime = autoafktimeout / 60.0;
-            
+
             // If `afk-timeout-command` in config.yml is empty, use default Essentials kicking behaviour instead of executing a command.
             if (ess.getSettings().getAfkTimeoutCommands().isEmpty()) {
                 this.getBase().kickPlayer(AdventureUtil.miniToLegacy(playerTl("autoAfkKickReason", kickTime)));
@@ -1112,7 +1112,7 @@ public String tlSender(String tlKey, Object... args) {
     }
 
     public Locale getPlayerLocale(final String locale) {
-        if (locale.equals(lastLocaleString)) {
+        if (locale == null || locale.equals(lastLocaleString)) {
             return playerLocale;
         }
         lastLocaleString = locale;