fix: Blank ('') no-permission messages shouldn't send blank lines (#5892)

patches/api/Make-the-default-permission-message-configurable.patch

@@ -51,7 +51,12 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
  
          if (permissionMessage == null) {
 -            target.sendMessage(ChatColor.RED + "I'm sorry, but you do not have permission to perform this command. Please contact the server administrators if you believe that this is a mistake.");
-+            target.sendMessage(Bukkit.getPermissionMessage()); // Paper
++            // Paper start
++            String bukkitPermissionMessage = Bukkit.getPermissionMessage();
++            if (org.apache.commons.lang.StringUtils.isNotBlank(bukkitPermissionMessage)) {
++                target.sendMessage(bukkitPermissionMessage);
++            }
++            // Paper end
          } else if (permissionMessage.length() != 0) {
              for (String line : permissionMessage.replace("<permission>", permission).split("\n")) {
                  target.sendMessage(line);