Start mobjnums at 1 instead of 0, so that the first found mobj can be relinked...

Start mobjnums at 1 instead of 0, so that the first found mobj can be relinked as a target etc to other mobjs properly

This fixes Brak's electric barrier disappearing for joiners to ERZC. There seems to be some issues with the lava falls there too I've found, but the electric barrier actually stays around now at least