What would happen if Xur leaves while you are viewing his inventory?

According to this question, Does Xur stay in the tower until you log out?, the answer states that Xur will appear and disappear at set times during the weekend.

What would happen if Xur leaves the tower while you are viewing his shop, or making a purchase?

I am never logged in during the time Xur logs out, so I am wondering if anybody has attempted this.

No, Xur will leave exactly when he is programmed to regardless of what you are doing. You can actually watch him phase in and phase out in real time.

If you are viewing his shop when it is time for him to leave he will disappear and your shop window will close.

Watch Xur disappear