Avoid read-outside-array error by QStringRef over-reach

Constructing a QStringRef directly from the string, offset and a
length is UB if the offset + length exceeds the string's length.
Thanks to Robert Loehning and libFuzzer for finding this.
QString::midRef (as correctly used in both changed uses of QStringRef,
since 432d3b69629) takes care of that for us.  Changed one UB case and
a matching but correct case, for consistency.

In the process, deduplicate a QStringList look-up.
Added tests to exercise the code (but the one that exercises the
formerly UB case doesn't crash before the fix, so isn't very useful;
the invalid read is only outside the array it's scanning, not outside
allocated memory).

Change-Id: I7051bbbc0267dd7ec0a8f75eee2034d0b7eb75a2
Reviewed-by: Anton Kudryavtsev <antkudr@mail.ru>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

0 files changed, 0 insertions, 0 deletions