some fixes

Author: dellis1972

src/Xamarin.Android.Build.Tasks/MSBuild/Xamarin/Android/Xamarin.Android.Bindings.Core.targets

@@ -145,13 +145,13 @@ It is shared between "legacy" binding projects and .NET 5 projects.
     <!-- Write a flag so we won't redo this target if nothing changed -->
     <Touch Files="$(_GeneratorStampFile)" AlwaysCreate="true" />
 
-    <ItemGroup>
+    <ItemGroup Condition=" '@(_GeneratedBindingFiles->Count())' != '0' ">
       <_ExistingGeneratedFiles Include="$(GeneratedOutputPath)**\*.cs" />
       <_ExistingGeneratedFiles Remove="@(_GeneratedBindingFiles)" />
     </ItemGroup>
 
     <!-- Delete any files which should not be there. -->
-    <Delete Files="@(_ExistingGeneratedFiles)" />
+    <Delete Files="@(_ExistingGeneratedFiles)" Condition=" '@(_ExistingGeneratedFiles->Count())' != '0' "/>
 
     <ItemGroup>
       <FileWrites Include="$(GeneratedOutputPath)**\*.cs" />