[pgs/subs] - fix pgs subs vanishing to early by initialising the pkt_timebase which was introduced in ffmpeg bump and which is used internally for calculating the pts of the pgs subs now
url: CURL::GetWithoutUserDetails would return non encoded hostname

For rar/zip and similar with an expected url encoded path in their
hostnames, CURL::GetWithoutUserDetails would return an invalidly
formatted non encoded hostname.