Ensure coherent response of ScrollDescendants

TypeError: byte indices must be integers or slices, not str
(1 additional frame(s) were not displayed)
...
  File "nxdrive\engine\watcher\remote_watcher.py", line 556, in _partial_full_scan
  File "nxdrive\engine\watcher\remote_watcher.py", line 138, in _scan_pair
  File "nxdrive\engine\watcher\remote_watcher.py", line 192, in _do_scan_remote
  File "nxdrive\engine\watcher\remote_watcher.py", line 242, in _scan_remote_scroll
  File "nxdrive\client\remote_client.py", line 367, in scroll_descendants

Unexpected error