My eyes aren't what they used to be I wish you would have used paint and drawn an arrow to it, but the bottom line is any crack will only get larger with continued use. If it's somewhere that you feel save enough to widen it by stressing the openng I would squirt a very small amount of supper glue into it and then hold it firmly together till it sets.
JMO Fabe
I think I seee it now it's on the hinge? Then the naswer is no it's not safe, and fixing it with super glue could be a bit tricky since you wouldn't want to put so much in the crack as to have it get down into where it needs to rotate.