Those two pieces (one on each side on top of the rear legs) are called "butterfly's" , they form part of the middle shell and are designed to stop the legs from moving up during flight maneuvers and causing a prop strike on the body.
If you can get the right industrial strength adhesive (maybe epoxy but it would depend on the type of plastic), you might be able to shore it up for a while, but it does look like its cracked through.
This issue was discovered a while back as the reason for a prop strike.
From what I remember, the Op replaced the butterfly's by himself, some others have done a carbon fiber mod gluing a piece on top.
G' evening everyone, I'm a new Mavic operator, my Ol Lady bought me this thing for Christmas. I've logged 10 hrs of flight time since then and have noticed some real bad prop strike when flying in Sport Mode. I would presume this is happening as I am descending and turning at full stick...
mavicpilots.com
Just out of interest do you do a lot of sport mode flying, as this was suspected as the cause ?