Fixed ulm_card_media_player_enable_volume_adjust in media player card

[r03l]

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
  I noticed that when the variable "ulm_card_media_player_enable_volume_adjust" was used in the media player card. The card would disappear from the UI. Furthermore, I noticed that value of "ulm_card_media_player_enable_volume_adjust" was not substracting in the case of volume down
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• I have followed the contribution guidelines
  • This PR is for a custom-card or documentation change and therefore directed to the main branch.
  • This PR is for a official card or any other directly to the integration related change and therefore directed to the release branch.