ITreeNode.GetContainingFile() is returning null after last SDK update

Please, provide test case where such situation happens.

So this is the code that the plugin runs against:

namespace TestClassLibrary.Business
{
public enum AddressType
{
Home = 0,
Work = 1,
Other = 2
}
}

It is in a file called "AddressType.cs"

When the cursor selects the enum name "AddressType"...

The plugin code runs:

Snippet

protected override Action<ITextControl> ExecutePsiTransaction(ISolution solution, IProgressIndicator progress)
{
     var enumDeclaration = _provider.GetSelectedElement<IEnumDeclaration>(true, true);Snippet

    var document = enumDeclaration.GetDocumentRange().Document;
    ... 
}

document is resulting in null since the last SDK update, because internally it is calling:

enumDeclaration.GetContainingFile() 

which also is returning null now (but didn't used to).

John, what is _provider? Better, to provide full sources of plugin so I can check without guessing.