Fix the issue in mouse click event

samples/python2/camshift.py

@@ -54,6 +54,7 @@ class App(object):
         if event == cv2.EVENT_LBUTTONDOWN:
             self.drag_start = (x, y)
             self.tracking_state = 0
+            return
         if self.drag_start:
             if flags & cv2.EVENT_FLAG_LBUTTON:
                 h, w = self.frame.shape[:2]