Well, You are in luck...If it works for you as it did to me. Just last week my brother dropped my Xinghen, and 2 corners broke like those in your pictures. At first I was uncertain what to do with it, but I super-glued them and they are as right as rain now (meaning working just fine with out any issues).
For gluing them, I would recommend that you add a decent amount of glue to the tip/inside the tip that is connected to the cube, as well as a little glue to the inside of the corner (inside the hole, and not on the outside) which should me obvious. After gluing it stick them together and let them sit for a bit to make sure that it is all solid before using. If for some reason the corner pops/breaks again then try it again and hopefully it works.
Please ask more questions if you have any.