QWebEngineView Asserts with navigation request for a new tab with qhc

If help file are qhc files and used with QtwebEngine it crashes when there is navigation request from HTML file (target="_bland") 

Attached example reproduces the problem:

Steps

- Compile attached demo in Debug-Mode.

• Copy included qhc-Files to the directory of HelpCrash.exe, so that helpCrash-Application can find them.
• Click in the table of content on "HelpPage1" on left side
• Inside the displayed Help-page click on a link. on right side
• An assertion with the problem will arise.

With Qt Version 5.9.2 there was no problem.