Fix Room.CopyFrom() skipping a field

Was making the close button not display when creating a room anew.

osu.Game/Online/Rooms/Room.cs

@@ -379,6 +379,7 @@ public void CopyFrom(Room other)
             Type = other.Type;
             MaxParticipants = other.MaxParticipants;
             ParticipantCount = other.ParticipantCount;
+            StartDate = other.StartDate;
             EndDate = other.EndDate;
             UserScore = other.UserScore;
             QueueMode = other.QueueMode;