Fix crash reported in https://bugs.kde.org/show_bug.cgi?id=338649#c20
related to multiple calls of m_source.unicode() where the calls return different address values. The solution is to call m_source.unicode() only once: lib/cppparser/lexer.h - In class Lexer add private member m_src of type const QChar*. lib/cppparser/lexer.cpp - In function Lexer::setSource, - assign m_source.unicode() to m_src; - if m_source.isEmpty() returns true then return without calling tokenize(). - In function Lexer::reset initialize m_src to null pointer. - In function Lexer::offset return m_src + offset. - In function Lexer::getOffset use m_src in lieu of src. This avoids the second call to m_source.unicode() which on newer Qt5 versions may return a different buffer. CCBUG: 338649