fix: enhance input file check

if user select camera as input, it will not check for file presence.

Author: Ahwar

main.py

@@ -111,7 +111,7 @@ def infer_on_stream(args):
  args.face_det_m, args.lmar_det_m, args.h_pose_m, args.g_est_m,
  args.input
  ]:
- if not Path(_).is_file():
+ if not Path(_).is_file() and str(_).upper() != "CAM":
  error_message = "This file is not Present: \"{}\" Check the file please".\
  format(_)
  logger.error(error_message)