QAction compile error on <Qt-5.7
QAction compile error on <Qt-5.7

Resolve semaphoreci CI build failure.

Starting with Qt-5.7, the parent parameter of QAction's constructor is
optional. However, to continue support for nvim-qt compile against older
versions of Qt, this parameter must be provided anyways.

equalsraf/neovim-qt,equalsraf/neovim-qt,equalsraf/neovim-qt,equalsraf/neovim-qt