- fix nullable warnings

Lib.Audio/Channel.cs

@@ -28,7 +28,7 @@ namespace Lib.Audio
         public IFader Fader { get; }
         public IKnob Knob { get; }
         public List<IButton> Buttons { get; }
-        public IControllable Controllable { get; private set; }
+        public IControllable? Controllable { get; private set; }
         
         public void AllocateControllable(IControllable controllable) => Controllable = controllable;
 
@@ -42,6 +42,6 @@ namespace Lib.Audio
             return buttons;
         }
         
-        private void OnFaderPositionChanged(object? sender, float position) => Controllable.SetVolume(position);
+        private void OnFaderPositionChanged(object? sender, float position) => Controllable?.SetVolume(position);
     }
 }

Lib.Audio/Controls/Fader.cs

@@ -21,6 +21,6 @@ namespace Lib.Audio.Controls
             }
         }
 
-        public event EventHandler<float> PositionChanged;
+        public event EventHandler<float>? PositionChanged;
     }
 }

Lib.Audio/Controls/Interfaces/IFader.cs

@@ -10,6 +10,6 @@ namespace Lib.Audio.Controls.Interfaces
     {
         float Position { get; } //TODO: float or double?
 
-        event EventHandler<float> PositionChanged;
+        event EventHandler<float>? PositionChanged;
     }
 }

Lib.Audio/Interfaces/IChannel.cs

@@ -14,7 +14,7 @@ namespace Lib.Audio.Interfaces
         IKnob Knob { get; }
         List<IButton> Buttons { get; }
         
-        IControllable Controllable { get; }
+        IControllable? Controllable { get; }
 
         void AllocateControllable(IControllable controllable);
     }