PQconnectdb/PQerrorMessage changed behavior on master

Hello,

While trying to use sqlsmith with postgres compiled from the master
branch, I've found that the PQerrorMessage() function now returns
non-informational but not empty error message after the successful
PQconnectdb() call.
    conn = PQconnectdb(conninfo.c_str());
    char *errmsg = PQerrorMessage(conn);
returns
'connection to server on socket "/tmp/ody8OuOaqV/.s.PGSQL.59860" failed: '

The affected sqlsmith code:
https://github.com/anse1/sqlsmith/blob/master/postgres.cc#L305

Best regards,
Alexander