Someone managed to snap off the screw heads which holds the latch. Your image is a bit hard to see things clearly, it’s also possible you are just missing the screws. I’ve see this a few times in the Mac Pro systems as well.
Here’s what it should look like
Often I find these have a thread sealer on them so its not easy to get the threaded piece out. See if you can apply a dremel tool with a very small and thin cutter to cut in a slot into the screw. The other option is getting a left hand drill to ease out the core via drilling in the middle the drill might catch and unscrew the core.
Finding a replacement latch will take some doing and you’ll still need to find the needed flathead screws that hold it on.
I found this one listed which is the complete setup: PowerMac G5 Case Latch Lever + Lock