A320 pilot reported hydraulic system malfunction during descent resulted in loss of autobrakes. Flight crew landed safely.

Narrative

In late cruise/early descent (this was a very short flight); we got an ECAM for 'HYD G SYS LO PR'; accompanied by a fault light on the PTU (Power Transfer Unit) switch on the overhead panel and an amber PTU indication on the HYD page. There were no ECAM actions associated with this fault; aside from a gravity gear extension and to apply landing distance procedure if hydraulic power is not regained. The green system showed normal pressure and fluid level; and there was no indication of failure of the #1 engine driven hydraulic pump. We both checked the FM for further information on this ECAM; and found none. The Captain asked me to request priority handling and ask for vectors while we troubleshot further and made a plan; which I did. Given that we saw normal pressure indications in this system; we opted to attempt an early normal gear extension prior to starting the approach rather than using the gravity extension system. The gear extended normally and gave down/locked indications both on the indicator near the gear handle and the wheel page on the lower ECAM. The Captain had been communicating the issue to the Dispatcher through ACARS; they ran landing numbers for Runway XXL for us. The Captain briefed the flight attendants and made an announcement to the passengers. ATC queried whether we wanted equipment standing by; which we opted to have. We flew a normal approach and landing; noting that the left engine reverser did deploy nomally. The autobrakes had disarmed when the ECAM first appeared and were not available. I did not catch whether spoilers 1+5 actually deployed; but they were showing amber rather than green. The landing was unremarkable; and we asked the fire trucks to follow us to the gate. We parked without incident. We noted that with both engines stopped; the green system showed 1800 PSI; which was impossible given that there were no operating hydraulic pumps. The Captain put in a maintenance report. We debriefed; and then met with the oncoming pilots to discuss what had happened. By the time I got to my hotel; the maintenance log had been closed out and the issue resolved.