Fixed plugin parameters not saved when device is disconnected

[mryhel]

Description

Summary of Changes:
InputPatch::getPluginParameters() and OutputPatch::getPluginParameters() returned an empty map when the plugin device was disconnected (m_plugin == NULL), causing all custom plugin parameters to be silently dropped when saving a workspace while the device is not connected.

m_parametersCache already existed and was used in reconnect(), but getPluginParameters() ignored it. This fix adds the missing fallback.

Related Issues: N/A

Checklist

• I have read and followed the QLC+ Coding Guidelines.
• My code adheres to the project's coding style, including:
  • Placing opening braces { on a new line for functions and class definitions.
  • Consistent use of spaces and indentation.
• I have tested my changes on the following platforms:
  • Linux
  • Windows
  • macOS
• I have added or updated documentation as necessary.

Testing

Test Cases:

1. Open a workspace with MIDI plugin parameters configured (init message, send note off, mode).
2. Disconnect the device and save the workspace.
3. Check the saved XML — verify parameters are present.

Test Results:

Before the fix — workspace opened with MIDI parameters configured, saved with device disconnected, parameters lost.

Was:

    <Input Plugin="MIDI" UID="None" Line="0" Profile="Akai APC Mini">
     <PluginParameters MIDISendNoteOff="false" initmessage="APC mini Ableton mode 2"/>
    </Input>
    <Output Plugin="DMX USB" UID="None" Line="0">
     <PluginParameters UniverseChannels="279"/>
    </Output>
    <Feedback Plugin="MIDI" UID="None" Line="1">
     <PluginParameters initmessage="APC mini Ableton mode 2" mode="Note Velocity"/>
    </Feedback>

Became:

    <Input Plugin="MIDI" UID="None" Line="0" Profile="Akai APC Mini"/>
    <Output Plugin="DMX USB" UID="None" Line="0"/>
    <Feedback Plugin="MIDI" UID="None" Line="1"/>

After the fix — same scenario, parameters preserved:

Was:

    <Input Plugin="MIDI" UID="None" Line="0" Profile="Akai APC Mini">
     <PluginParameters MIDISendNoteOff="false" initmessage="APC mini Ableton mode 2"/>
    </Input>
    <Output Plugin="DMX USB" UID="None" Line="0">
     <PluginParameters UniverseChannels="279"/>
    </Output>
    <Feedback Plugin="MIDI" UID="None" Line="1">
     <PluginParameters initmessage="APC mini Ableton mode 2" mode="Note Velocity"/>
    </Feedback>

Became:

    <Input Plugin="MIDI" UID="None" Line="0" Profile="Akai APC Mini">
     <PluginParameters MIDISendNoteOff="false" initmessage="APC mini Ableton mode 2"/>
    </Input>
    <Output Plugin="DMX USB" UID="None" Line="0">
     <PluginParameters UniverseChannels="279"/>
    </Output>
    <Feedback Plugin="MIDI" UID="None" Line="1">
     <PluginParameters initmessage="APC mini Ableton mode 2" mode="Note Velocity"/>
    </Feedback>

[coveralls]

coverage: 34.05% (+0.002%) from 34.048% — mryhel:fix_5_plugin_params into mcallegari:master