When the content of a manual page does not specify a section, the

When the content of a manual page does not specify a section, the
empty string got added to the list of sections, breaking the database
format slightly and causing the page to not be considered part of
any section, not even if a section could be deduced from the directory
or from the file name.
Bug found due to the bogus pcredemo(3) "manual" in the pcre-8.38p0 package.