macbook pro stuck after I turned off HDMI external display

Hi,

I have a Late 2013 Macbook Pro running El Capitan 10.11.1. Recently I have bought a HP 23 inch display and connected its HDMI to my Macbook Pro.

It works fine when the display is turned on. But I found that if I keep the HDMI wire connected and turned off the display (sometimes I only need one display to work), the Mac OS begins to get stuck periodically (you will see it if you move your mouse continuously). This prevents me to work seriously. I don't know if this is a serious bug of Mac OS. If it is, is it possible to fix it? Thanks very much!

xiexinyls