That’s unfortunately a known issue with the built in WebBrowser component. This is a wrapped component from the OS, and seems to be an ancient IE component, which is sometimes updated, but often not.
If you search for “Projucer script error” or similar names, you will find many hits, e.g.
The best solution seems not to log in and use the GPL version (set the define and recompile), a bit sad answer though…
