ArgumentOutOfRange exception while creating completion item #969

   at System.Char.IsLetter(String s, Int32 index)
   at Microsoft.Python.LanguageServer.Completion.CompletionItemSource.CreateCompletionItem(String text, CompletionItemKind kind)
   at System.Linq.Enumerable.SelectEnumerableIterator`2.MoveNext()
   at System.Collections.Generic.LargeArrayBuilder`1.AddRange(IEnumerable`1 items)
   at System.Collections.Generic.EnumerableHelpers.ToArray[T](IEnumerable`1 source)
   at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
   at Microsoft.Python.LanguageServer.Completion.ImportCompletion.TryGetCompletions(ImportStatement import, CompletionContext context)
   at Microsoft.Python.LanguageServer.Completion.CompletionSource.GetCompletions(IDocumentAnalysis analysis, SourceLocation location)
   at Microsoft.Python.LanguageServer.Implementation.Server.Completion(CompletionParams params, CancellationToken cancellationToken)
   at Microsoft.Python.LanguageServer.Implementation.LanguageServer.Completion(JToken token, CancellationToken cancellationToken)