PostgreSQL: memory leak in QPSQLDriverPrivate::getPSQLVersion()

After migrating from 5.2.1 to 5.5.1 we noticed >1GB leak per 12h at server software making about 10-20 connections to PostgreSQL database per second. After some investigation I've found leak here:

http://code.qt.io/cgit/qt/qtbase.git/tree/src/sql/drivers/psql/qsql_psql.cpp?h=5.5#n760

result variable is overwritten without releasing it's previous resource.

There is another question - why this block is entered in the first place if I'm using PostgreSQL and libpq5 from pgdg repository with version 9.4.5:

apt-cache policy libpq5
libpq5:
  Installed: 9.4.5-1.pgdg14.04+1
  Candidate: 9.4.5-1.pgdg14.04+1
  Version table:
 *** 9.4.5-1.pgdg14.04+1 0
        500 http://apt.postgresql.org/pub/repos/apt/ trusty-pgdg/main amd64 Packages
        100 /var/lib/dpkg/status
     9.3.10-0ubuntu0.14.04 0
        500 http://lt.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu/ trusty-security/main amd64 Packages
     9.3.4-1 0
        500 http://lt.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages

Maybe it's something to do with ifdefs above on Qt build server environment? If I build libsqlpsql.so in Debian 7 machine using packages from apt.postgresql.org, there is no leak.