C#: Upgrade nuget packages

Author: tamasvajk

csharp/autobuilder/Semmle.Autobuild.CSharp/DotNetRule.cs

@@ -145,7 +145,7 @@ private static BuildScript DownloadDotNet(Autobuilder builder, string installDir
                 try
                 {
                     var o = JObject.Parse(File.ReadAllText(path));
-                    version = (string)o["sdk"]["version"];
+                    version = (string)(o?["sdk"]?["version"]!);
                 }
                 catch  // lgtm[cs/catch-of-all-exceptions]
                 {

csharp/autobuilder/Semmle.Autobuild.CSharp/Semmle.Autobuild.CSharp.csproj

@@ -17,8 +17,8 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.Build" Version="16.0.461" />
-    <PackageReference Include="Newtonsoft.Json" Version="12.0.2" />
+    <PackageReference Include="Microsoft.Build" Version="16.9.0" />
+    <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
   </ItemGroup>
 
   <ItemGroup>

csharp/autobuilder/Semmle.Autobuild.Shared/Semmle.Autobuild.Shared.csproj

@@ -14,7 +14,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.Build" Version="16.0.461" />
+    <PackageReference Include="Microsoft.Build" Version="16.9.0" />
   </ItemGroup>
 
   <ItemGroup>

csharp/extractor/Semmle.Extraction.CSharp.Standalone/Semmle.Extraction.CSharp.Standalone.csproj

@@ -23,7 +23,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.Build" Version="16.0.461" />
+    <PackageReference Include="Microsoft.Build" Version="16.9.0" />
     <PackageReference Include="Microsoft.Win32.Primitives" Version="4.3.0" />
     <PackageReference Include="System.Net.Primitives" Version="4.3.1" />
     <PackageReference Include="System.Security.Principal" Version="4.3.0" />