There are a few instances where Tools/TestWebKitAPI/Tests/WebKitGLib/TestUIClient.cpp uses "*foo = value" instead of "foo = value" to set a value into a std::optional. This is using "operator*" which returns a reference to the contained value, and then assigning to it. Dereferencing a std::optional without a contained value is undefined behaviour, and triggers C++ library assertions (see bug #266396).