use `self.highlight:handleEvent(Event:new("Tap"))` instead of
`self.ui:handleEvent(Event:new("Tap"))` when clearing highlighted
text since Tap event in latter situation will be captured by
the dogear widget.
This should finish the work to make all globals to local variables.
That allows LuaJIT to properly compile things by interning the
references to the relevant parts (rather than looking up globals
all the time which stops a trace).
