You can ignore this bug, since it's not a bug. We found it in the official
documentation https://www.postgresql.org/docs/9.5/static/release-9-5.html
once we reported it.
At first we thought it was a bug with the '||' operator, so we couldn't
find it in the documentation, then while we were reporting it we realized
it is a change in operator precedence. We mostly checked the
https://wiki.postgresql.org/wiki/What's_new_in_PostgreSQL_9.5 for new
changes, but in there it wasn't mention.
Sorry about this and thanks for the operator_precedence_warning, it will
help a lot.