It might be a variation of
MDEV-414, but since it only seems to affect 5.5, I'm filing it separately.
On 5.3, this SELECT produces a warning:
It might be a bit strange that it has an error inside, but it worked the same way in MySQL 5.1, only the code was different:
In MySQL 5.5, it's a more traditional warning:
But in MariaDB 5.5, no warning at all.