Require investigation in possible zero-devision problem

[zichongy]

Processing file:  0003.npy
C:\Users\zicho\Projects\calculate-joint-angles\utils.py:69: RuntimeWarning: invalid value encountered in double_scalars
  R = np.eye(3) + vx + vx@vx*((1-c)/s**2)

Processing file:  0083.npy
.\calculate_joint_angles.py:140: RuntimeWarning: invalid value encountered in divide
  root_u = root_u/np.sqrt(np.sum(np.square(root_u)))

Processing file:  0086.npy
C:\Users\zicho\Projects\calculate-joint-angles\utils.py:59: RuntimeWarning: invalid value encountered in divide
  uB = B/np.sqrt(np.sum(np.square(B)))

Processing file:  0091.npy
C:\Users\zicho\Projects\calculate-joint-angles\utils.py:69: RuntimeWarning: divide by zero encountered in double_scalars
  R = np.eye(3) + vx + vx@vx*((1-c)/s**2)
C:\Users\zicho\Projects\calculate-joint-angles\utils.py:69: RuntimeWarning: invalid value encountered in multiply    
  R = np.eye(3) + vx + vx@vx*((1-c)/s**2)

Processing file:  2173.npy
.\calculate_joint_angles.py:142: RuntimeWarning: invalid value encountered in divide
  root_v = root_v/np.sqrt(np.sum(np.square(root_v)))

[zichongy]

This may be somehow related to PennAction's low fps, which would cause sudden changes in joint angles.

[zichongy]

This commit added support to filter out all videos with joints marked as (0.75, 0.75) which probably means they are occluded or out of frame.
7caced6