Update detect.py (#2167)

Without this cv2.imshow opens a window but nothing is visible

Update detect.py (#2167)
c32b0aff · ab-101 · GitHub · a5359f6c · c32b0aff
--- a/detect.py
+++ b/detect.py
@@ -118,6 +118,7 @@ def detect(save_img=False):
            # Stream results
            if view_img:
                cv2.imshow(str(p), im0)
+                cv2.waitKey(1) # 1 millisecond
            # Save results (image with detections)
            if save_img: