fix: fail safely if unable to get player status (Media Control)

[sudoAlphaX]

Description

In come cases where there exists a registered MPRIS player that
doesn't have support for playerstatus, safeeyes errors and doesnt
launch a break when the Media Control plugin is enabled.

This patch adds a check to the mediacontrol plugin that checks
if "PlaybackStatus" cached_property is not None, and only then attempts
to get media playing status.

Steps to reproduce:

1. Install playerctl
2. Launch playerctld
3. Do not play any media (close all media playing apps)
4. Try to launch a break using safeeyes

Error:

  File "/usr/lib/python3.13/site-packages/safeeyes/utility.py", line 106, in <lambda>
    GLib.idle_add(lambda: target_function(*args, **kwargs))
                          ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.13/site-packages/safeeyes/core.py", line 277, in __fire_start_break
    self.start_break.fire(break_obj)
    ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^
  File "/usr/lib/python3.13/site-packages/safeeyes/model.py", line 293, in fire
    if not handler(*args, **keywargs):
           ~~~~~~~^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.13/site-packages/safeeyes/safeeyes.py", line 356, in start_break
    actions = self.plugins_manager.get_break_screen_tray_actions(break_obj)
  File "/usr/lib/python3.13/site-packages/safeeyes/plugin_manager.py", line 209, in get_break_screen_tray_actions
    action = plugin['module'].get_tray_action(break_obj)
  File "/usr/lib/python3.13/site-packages/safeeyes/plugins/mediacontrol/plugin.py", line 89, in get_tray_action
    players = __active_players()
  File "/usr/lib/python3.13/site-packages/safeeyes/plugins/mediacontrol/plugin.py", line 62, in __active_players
    status = player.get_cached_property('PlaybackStatus').unpack().lower()
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'unpack'

Expected Behaviour:

Doesn't crash

[deltragon]

From what I can tell, the specification does require this property - but I might be reading that wrong, and either way, it doesn't hurt to be more crash-resilient.
LGTM, thanks for the PR.

[sudoAlphaX]

That's what even I thought, but it seems something is weird with playerctl causing it to be a MPRIS player.

The problem is, it doesnt show up in playerctl status or `playerctl metdata', leading one to believe it is not a player. But applications (specifically python, havent tested with others) report playerctld as a player.

Trackma is a list tracker application I use written in python. Here is what it reports:

I will check further why playerctld is doing something like this.

Thanks for merging btw.