Some accessibility settings (e.g. VoiceOver is one) trigger a crash at startup.  The problem is that in quiview_accessibility.mm, function 'indexOfAccessibilityElement' does this...

return [m_accessibleElements indexOfObject:element];

...without checking to see whether 'm_accessibleElements' has anything in it.  I expect that this happens in newer Qt versions as well.

Apple's documentation says that 'indexOfAccessibilityElement' should return "NSNotFound if the element does not exist."  So a simple check would alleviate the exception.  Whether it's a logical problem for this array to be empty here I don't know.