Merge pull request #12070 from tvsonar/bugfix-nullref

Bugfix: possible NRE in TypeNameSerializer extensions

src/Compilers/Core/Portable/PEWriter/TypeNameSerializer.cs

@@ -179,7 +179,7 @@ private static void AppendAssemblyQualifierIfNecessary(StringBuilder sb, ITypeRe
             IManagedPointerTypeReference reference = typeReference as IManagedPointerTypeReference;
             if (reference != null)
             {
-                AppendAssemblyQualifierIfNecessary(sb, pointer.GetTargetType(context), out isAssemQualified, context);
+                AppendAssemblyQualifierIfNecessary(sb, reference.GetTargetType(context), out isAssemQualified, context);
                 return;
             }