Don't send error when joining for the first time

src/main/java/de/epiceric/shopchest/listeners/NotifyPlayerOnJoinListener.java

@@ -38,8 +38,7 @@ public class NotifyPlayerOnJoinListener implements Listener {
             @Override
             public void onResult(Long result) {
                 if (result < 0) {
-                    p.sendMessage(LanguageUtils.getMessage(Message.ERROR_OCCURRED,
-                            new Replacement(Placeholder.ERROR, "Could not get last time you logged out")));
+                    // No logout saved, probably first time joining.
                     return;
                 }
 

src/main/java/de/epiceric/shopchest/sql/Database.java

@@ -543,6 +543,7 @@ public abstract class Database {
      * @param player   Player who logged out
      * @param callback Callback that - if succeeded - returns the time in
      *                 milliseconds the player logged out (as {@code long})
+     *                 or {@code -1} if the player has not logged out yet.
      */
     public void getLastLogout(final Player player, final Callback<Long> callback) {
         new BukkitRunnable() {