.data() in both classes has a null pointer check so it will return non-
null even if the object is storing a null pointer, for compatibility
with Qt 5 (controlled by QT5_NULL_STRINGS). We don't need this in
first()/last()/sliced()/chopped(), so we can skip the test and pass
whatever pointer it is directly to the class constructor. Both of them
handle null pointers creating an isNull() object.
This is a minor performance optimization and interestingly makes these
functions now retain isNull() with the result. I'm not adding test for
that as I don't want to hardcode that they will do so.
Change-Id: Ifeb6206a9fa04424964bfffd17888d14ec8244ec
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
2b7c2c3a71