Rengar passive bug with wards

I was playing rengar against a nasus top lane. I was hiding the the middle brush when nasus warded it. Since I was in the brush I jumped to the ward and rengar started auto attacking it. After my first auto attack the ward dissapeared but rengar continued to auto attack. After 2 more autos I killed the ward. To be noted, I did not click after I first clicked on the ward, Rengar just auto attacked the air by himself.