Clazy Warning Global Static

[jgehrig]

TODO Tag in Code!

See app.cpp:
std::vector<MainWindow*> s_windows;

This code throws a Clazy warning because the CTOR is non-trivial.

Here is an alternative:

std::vector<MainWindow*>& GetWindowList() noexcept
{
  static `std::vector<MainWindow*> s_windows;`
  return s_windows;
}

// Replace all usage of "s_windows" with "GetWindowList()"

Open to other solutions too :)

[jgehrig]

Optional:

Remove the other global statics. Global statics can cause all sorts of interesting issues...

Some people consider global statics a "code smell". If we can remove them easily, perhaps this is a good idea?