Streamcontinuitymanager error

*I'm submitting a ...*
- [x] bug report

## General information

### Prerequisites

* [x] Are you running the latest version?

### Description

Getting an error popup when starting a TV episode "Netflix Streamincontinuitymanager disabled ..."

### Steps to Reproduce

1. Start episode
2. error pops up: "Netflix Streamincontinuitymanager disabled ..."
3. vanishes before I can read the whole scrolling text

**Expected behavior:** [What you expected to happen]

**Actual behavior:** [What actually happened]

## Context (Environment)

### Installation

* [ ] 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

#### Additional information on the environment

Netflix 1.2.0, Kodi 18.6, CoreElec 9.2.2, Odroid-C2

## Debug log

[pastebin](https://pastebin.com/jcn8e0pa)

## Other information

The log shows an error in
`File "/storage/.kodi/addons/plugin.video.netflix/resources/lib/services/playback/stream_continuity.py", line 250, in _show_only_forced_subtitle`

workaround / temporary fix:
when I disable "Disable subtitles if there are no forced subtitles..." in the addons settings, the error goes away.

Start at resources/lib/services/playback/stream_continuity.py line 250, _show_only_forced_subtitle, and review the linked debug log. Reproduce playback with “Disable subtitles if there are no forced subtitles...” enabled, then verify that starting an episode no longer shows the Streamcontinuitymanager error.

Written by the indexing model from the issue text.