[ticket/12433] Use a different message when nesting of quotes is not allowed

PHPBB3-12433
Merge pull request #2463 from nickvergessen/ticket/12433

[ticket/12433] Use a different message when nesting of quotes is not allowed

* nickvergessen/ticket/12433:
  [ticket/12433] Use a different message when nesting of quotes is not allowed
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12433] Use a different message when nesting of quotes is not allowed