Error when go to definition of PyQt5's module #440

I have code like following

from PyQt5.QtChart import QChart, QChartView, QLineSeries, QValueAxis
from PyQt5.QtWidgets import QApplication, QTabWidget, QVBoxLayout, QWidget

When I go to the definition of PyQt5.QtChart or PyQt5.QtWidgets, then VSCode popup
the OUTPUT panel and print like following

[Error - 7:18:34 PM] Request textDocument/definition failed.
Message: Value cannot be null.
Parameter name: source
Code: -32000
at System.Linq.Enumerable.Select[TSource,TResult](IEnumerable1 source, Func2 selector)
at Microsoft.Python.LanguageServer.Implementation.Server.GetModuleReferences(IPythonProjectEntry entry, PythonAst tree, BufferVersion version, ReferencesParams params)
at Microsoft.Python.LanguageServer.Implementation.Server.FindReferences(ReferencesParams params, CancellationToken cancellationToken)
at Microsoft.Python.LanguageServer.Implementation.Server.GotoDefinition(TextDocumentPositionParams params, CancellationToken cancellationToken)
at Microsoft.Python.LanguageServer.Implementation.LanguageServer.GotoDefinition(JToken token, CancellationToken cancellationToken)