To interpolated string throws NullReferenceException

[MSeifert04]

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When I open the refactorings (Ctrl + .) on code like this:

string.Format(CultureInfo.InvariantCulture, "The {0} is here", "fun");

it throws a NRE:

System.NullReferenceException : Object reference not set to an instance of an object.
   at RefactoringEssentials.CSharp.CodeRefactorings.ConvertStringFormatToInterpolatedStringCodeRefactoringProvider.CreateInterpolatedString(InvocationExpressionSyntax invocation)
   at RefactoringEssentials.CSharp.CodeRefactorings.ConvertStringFormatToInterpolatedStringCodeRefactoringProvider.<>c__DisplayClass0_0.<ComputeRefactoringsAsync>b__0(CancellationToken t)
   at RefactoringEssentials.DocumentChangeAction.GetChangedDocumentAsync(CancellationToken cancellationToken)
   at async Microsoft.CodeAnalysis.CodeActions.CodeAction.GetChangedSolutionAsync(<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.CodeActions.CodeAction.ComputeOperationsAsync(<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.CodeActions.CodeAction.ComputePreviewOperationsAsync(<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.CodeActions.CodeAction.GetPreviewOperationsAsync(<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.Editor.Implementation.Suggestions.SuggestedAction.GetPreviewResultAsync(<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.Editor.Implementation.Suggestions.SuggestedActionWithNestedFlavors.<>c__DisplayClass11_0.<GetPreviewAsync>b__0(<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.Extensions.IExtensionManagerExtensions.PerformFunctionAsync[T](<Unknown Parameters>)