Bug: "TypeError: string indices must be integers" retrieving list of seasons/episodes

Using the search dialog, I look for "The 100" and receive a very long list of show titles, that starts off with "The 100" and "The 100 Years Show".
When I click on the 1st show title, I see a generic failure message and in the kodi.log:

```
16:44:00.781 T:140044855531264 ERROR: EXCEPTION Thrown (PythonToCppException) : -->Python callback/script returned the following error<--
- NOTE: IGNORING THIS CAN LEAD TO MEMORY LEAKS!
Error Type:
Error Contents: string indices must be integers
Traceback (most recent call last):
File "/storage/.kodi/addons/plugin.video.netflix/addon.py", line 33, in
NAVIGATION.router(paramstring=REQUEST_PARAMS)
File "/storage/.kodi/addons/plugin.video.netflix/resources/lib/utils.py", line 60, in wrapped
result = func(*args, **kwargs)
File "/storage/.kodi/addons/plugin.video.netflix/resources/lib/Navigation.py", line 174, in router
widget_display=widget_display)
File "/storage/.kodi/addons/plugin.video.netflix/resources/lib/Navigation.py", line 465, in show_seasons
d = [(v['idx'], k) for k, v in season_list.items()]
TypeError: string indices must be integers
-->End of Python script error report<--
16:44:00.984 T:140044855531264 WARNING: CPythonInvoker(5, /storage/.kodi/addons/plugin.video.netflix/addon.py): the python script "/storage/.kodi/addons/plugin.video.netflix/addon.py" has left several classes in memory that we couldn't clean up. The classes include: N9XBMCAddon9xbmcaddon5AddonE
16:44:00.996 T:140045159741184 ERROR: GetDirectory - Error getting plugin://plugin.video.netflix/?action=season_list&pin=True&show_id=70283264&tvshowtitle=VGhlIDEwMA%3d%3d
16:44:01.013 T:140046242883712 ERROR: CGUIMediaWindow::GetDirectory(plugin://plugin.video.netflix/?action=season_list&pin=True&show_id=70283264&tvshowtitle=VGhlIDEwMA%3d%3d) failed
```
I installed 0.13.21 from the Netflix Repo on LE 8.95.5 (I got network issues with 9.0.0) on a generic x86/x64.

* [ ] I installed the plugin via zip from the Releases page
* [X] I´m using the Netflix Repo
* [ ] I´m using a different source (Please tell which)

### Operating System

* [X] Linux (x86/x64)
* [ ] OSX (x86/x64)
* [ ] Windows (x86/x64)
* [ ] Linux (ARM)
* [ ] Android

Start in resources/lib/Navigation.py at show_seasons, especially line 465 where season_list entries are indexed, and reproduce the search for "The 100" from the issue. Inspect the season_list data returned for show_id 70283264; done means selecting the show opens its seasons without the TypeError or generic failure.

Written by the indexing model from the issue text.