[ticket/10442] Adds <dd>&nbsp;</dd> to <dl> for xhtml correctness

PHPBB3-10442
Merge pull request #3164 from Crizz0/ticket/10442

[ticket/10442] Adds <dd>&nbsp;</dd> to <dl> for xhtml correctness
Merge branch 'develop-olympus' into develop-ascraeus
Merge branch 'develop-ascraeus' into develop