[ticket/12083] Fix Select All in CODE bbcode with only one char

PHPBB3-12083
Merge remote-tracking branch 'vsephpbb/ticket/12083' into develop-ascraeus

* vsephpbb/ticket/12083:
  [ticket/12083] Fix Select All in CODE bbcode with only one char
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12083] Fix Select All in CODE bbcode with only one char