Add ability to remove image

Wallet.Avalonia/CreateWalletView.axaml

@@ -85,7 +85,10 @@
                     <DropDownButton.Flyout>
                         <MenuFlyout>
                             <MenuItem Command="{Binding ImportCommand}" Header="Import image" />
-                            <MenuItem Header="Remove image" />
+                            <MenuItem
+                                Command="{Binding RemoveCommand}"
+                                Header="Remove image"
+                                IsEnabled="{Binding ImageDescriptor, Converter={x:Static ObjectConverters.IsNotNull}}" />
                         </MenuFlyout>
                     </DropDownButton.Flyout>
                     <TextBlock

Wallet/CreateWalletViewModel.cs

@@ -65,6 +65,9 @@ public partial class CreateWalletViewModel :
     public async Task Import() => ImageDescriptor = await Mediator.Handle<CreateEventArgs<ProfileImage>,
         IImageDescriptor>(Create.As<ProfileImage>());
 
+    [RelayCommand]
+    public void Remove() => ImageDescriptor = null;
+
     protected override void OnPropertyChanged(PropertyChangedEventArgs args)
     {
         if (args.PropertyName is string name)