overflow structure

i noticed, the glass behind my overflow has a chip in it, right along the edge... being held in place by the silicone at the seam. otherwise the chip would fall out. its a circle shape.
is the glass behind the plastic wall for structure?
i'm wonder if i need to worry about it, i have no idea how long its been like that.
on the other side of this black wall, about where the circle is drawn.
Attachment 118888

Is the chip on the back panel of the aquarium, or somewhere in the overflow chamber?

its in the overflow chamber.....were to pieces of glass come together. i can't get pic at moment