fix: mediaplayer attribute error

[Gh0stExp10it]

Fix regarding the issues with the MediaPlayer AttributeError: #67

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Copied text from Issue:

I have analysed the problem a little more. It definitely has something to do with the plugin for controlling Samsung Smart TVs. Unfortunately, this third-party plugin keeps clearing the current playback status. Thus the source_list is not equal to the current_source. Here is an excerpt from the log, which I have expanded a little.

Source List from my Configuration

19:26:05 ERROR (homeassistant.py): Attributes: {'source_list': ['TV', 'Unbekannt (HDMI 1)', 'Unbekannt (HDMI 2)', 'Unbekannt (HDMI 3)', 'ARD-Mediathek', 'ARTE', 'Amazon Prime', 'Joyn', 'Netflix', 'Plex', 'Spotify', 'YouTube', 'ZDF-Mediathek', '01| ARD', '02| ZDF', '03| RTL', '04| Sat.1', '05| ProSieben', '06| RTL ZWEI', '07| Kabel Eins', '08| VOX', '09| SUPER RTL', '10| ProSieben MAXX', '11| DMAX'] [...]

Actual Source, which falls back to the app_id

19:26:05 ERROR (homeassistant.py): Attributes: {[...] 'media_title': 'Das Erste HD', 'app_id': 'TV/HDMI', 'source': 'TV/HDMI', [...]

The source list does not contain any attribute that refers to the actual source == TV/HDMI
The error therefore only affects the control of the radiobox-marked icon and text Currently selected Source. As a simple fix, I would suggest an additional check using the source_list list. I will create a PR, then the original author can check this again.

[Garulf]

Thank you for fixing this.