Unauthorized external character with openCV

Question

I am trying to initialize OpenNI sensors using OpenCV to get a depth map from the depth sensor of my kinect.

code I used one depth image:

and the output I get is:

LNK2019: unresolved external symbol "int __cdelc cv::waitKey(int)" ( ?waitKey@cv @@ YAHH@Z ) reference in function _main 

In the .pro file, I have:

 QT += widgets WITH_OPENNI = ON