Allow ResolutionScope to be nil

Commit migrated from https://github.com/dotnet/corefx/commit/bc3775f1dccc80a11605b794296aa54037420713

src/libraries/System.Reflection.Metadata/src/System/Reflection/Metadata/Ecma335/MetadataBuilder.Tables.cs

@@ -375,7 +375,7 @@ private static void SetTableCapacity<T>(List<T> table, int rowCount)
         /// </summary>
         /// <param name="resolutionScope">
         /// The entity declaring the target type: 
-        /// <see cref="ModuleDefinitionHandle"/>, <see cref="ModuleReferenceHandle"/>, <see cref="AssemblyReferenceHandle"/> or <see cref="TypeReferenceHandle"/>.
+        /// <see cref="ModuleDefinitionHandle"/>, <see cref="ModuleReferenceHandle"/>, <see cref="AssemblyReferenceHandle"/>, <see cref="TypeReferenceHandle"/>, or nil.
         /// </param>
         /// <param name="namespace">Namespace.</param>
         /// <param name="name">Type name.</param>
@@ -390,7 +390,7 @@ private static void SetTableCapacity<T>(List<T> table, int rowCount)
 
             _typeRefTable.Add(new TypeRefRow
             {
-                ResolutionScope = CodedIndex.ResolutionScope(resolutionScope),
+                ResolutionScope = resolutionScope.IsNil ? 0 : CodedIndex.ResolutionScope(resolutionScope),
                 Name = name,
                 Namespace = @namespace
             });