Error 'character must be non-negative' when filtering

[bottom-feeder]

Describe the bug
When I filter the XML with an xpath expression '//node()[@Product]', the filtering works, highlighting all nodes with the attribute 'product'. However, when I want to find all nodes without this attribute by applying the expression '//node()[not(@Product)]', I get the error 'illegal argument: character must be non-negative'. I see several found nodes in the first few dozen lines in the output. Nothing gets highlighted.

Desktop (please complete the following information):

• OS: Win10
• Browser: Chrome
• Xpath Tester Version: v1.2.0