Avoid null reference exceptions

src/Yavsc/Helpers/AsciiDocHelpers.cs

@@ -90,11 +90,11 @@ namespace Yavsc.Helpers
 
                 case "AsciiDocNet.TextLiteral":
                     var tl = elt as TextLiteral;
-                   if (tl.Attributes.Anchor!=null)
+                   if (tl?.Attributes.Anchor!=null)
                    {
                          sb.AppendFormat("<a name=\"{0}\">{1}</a> ", tl.Attributes.Anchor.Id, tl.Attributes.Anchor.XRefLabel);
                    }
-                    sb.Append(tl.Text);
+                   if (tl!=null) sb.Append(tl.Text);
                     break;
 
                 case "AsciiDocNet.Emphasis":

src/Yavsc/Yavsc.csproj

@@ -42,7 +42,7 @@
     <PackageReference Include="Microsoft.AspNetCore.Antiforgery" Version="2.2.0" />
     <PackageReference Include="Swashbuckle.AspNetCore" Version="6.5.0" />
     <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" Version="8.0.2" IncludeAssets="All" />
-    <PackageReference Include="AsciiDocNet" Version="1.0.0" />
+    <PackageReference Include="AsciiDocNet" Version="1.0.0-alpha6" />
 
     <PackageReference Include="SixLabors.ImageSharp" Version="3.1.6" />
   </ItemGroup>