Topic with no poll is being considered as having poll on editing

Discussion: https://www.phpbb.com/community/viewtopic.php?p=14593966#p14593966
In short: While editing a 1st post of a topic with no poll, error is thrown on submitting: You must enter at least two poll options.
The cause: in 3.2.x the empty poll title is not actually empty but <t></t> which is considered by system as non-empty poll title, because the value tested for emptyness is taken directly from the database (https://github.com/phpbb/phpbb/blob/master/phpBB/posting.php#L1181).