A couple fixes for the audio backend GUI option (#1360)

* Detect available audio backends in the gui on a separate thread and

hardcode dummy backend in the dropdown and select it by default

* Use a Task rather than a Thread

* Modify UI on UI thread

Ryujinx/Ui/SettingsWindow.cs

@@ -11,6 +11,7 @@ using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Reflection;
+using System.Threading.Tasks;
 
 using GUI = Gtk.Builder.ObjectAttribute;
 
@@ -198,15 +199,32 @@ namespace Ryujinx.Ui
                 _systemTimeZoneSelect.Append(locationName, locationName);
             }
 
-            _audioBackendSelect.Append(AudioBackend.Dummy.ToString(), AudioBackend.Dummy.ToString());
-            if (SoundIoAudioOut.IsSupported)
-                _audioBackendSelect.Append(AudioBackend.SoundIo.ToString(), "SoundIO");
-            if (OpenALAudioOut.IsSupported)
-                _audioBackendSelect.Append(AudioBackend.OpenAl.ToString(), "OpenAL");
+            Task.Run(() =>
+            {
+                if (SoundIoAudioOut.IsSupported)
+                {
+                    Application.Invoke(delegate
+                    {
+                        _audioBackendSelect.Append(AudioBackend.SoundIo.ToString(), "SoundIO");
+                    });
+                }
+
+                if (OpenALAudioOut.IsSupported)
+                {
+                    Application.Invoke(delegate
+                    {
+                        _audioBackendSelect.Append(AudioBackend.OpenAl.ToString(), "OpenAL");
+                    });
+                } 
+
+                Application.Invoke(delegate
+                {
+                    _audioBackendSelect.SetActiveId(ConfigurationState.Instance.System.AudioBackend.Value.ToString());
+                });
+            });
 
             _systemLanguageSelect.SetActiveId(ConfigurationState.Instance.System.Language.Value.ToString());
             _systemRegionSelect.SetActiveId(ConfigurationState.Instance.System.Region.Value.ToString());
-            _audioBackendSelect.SetActiveId(ConfigurationState.Instance.System.AudioBackend.Value.ToString());
             _systemTimeZoneSelect.SetActiveId(timeZoneContentManager.SanityCheckDeviceLocationName());
             _resScaleCombo.SetActiveId(ConfigurationState.Instance.Graphics.ResScale.Value.ToString());
             _anisotropy.SetActiveId(ConfigurationState.Instance.Graphics.MaxAnisotropy.Value.ToString());

Ryujinx/Ui/SettingsWindow.glade

@@ -1494,6 +1494,10 @@
                                     <property name="can_focus">False</property>
                                     <property name="tooltip_text" translatable="yes">Change Audio Backend</property>
                                     <property name="margin_left">5</property>
+                                    <property name="active_id">Dummy</property>
+                                    <items>
+                                      <item id="Dummy" translatable="yes">Dummy</item>
+                                    </items>
                                   </object>
                                   <packing>
                                     <property name="expand">False</property>