I moved m_engine creation to the constructor.
However, it is not complete until after calling m_engine->Create().
The UT segfault because the pointer is not null and destructor calls
m_engine->Destroy() on an incomplete object.
(Yes, UTs test incomplete SUT.)

So I moved back the m_engine creation to CApp::Create() but before
the SDL initialization as m_engine holds the flag for vsync.