fixes: Mark FocusManager and InputManager  as nullable
fixes: Mark FocusManager and InputManager  as nullable

AvaloniaUI/Avalonia,wieslawsoltes/Perspex,SuperJMN/Avalonia,wieslawsoltes/Perspex,grokys/Perspex,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,AvaloniaUI/Avalonia,SuperJMN/Avalonia,SuperJMN/Avalonia,AvaloniaUI/Avalonia,SuperJMN/Avalonia,wieslawsoltes/Perspex,SuperJMN/Avalonia,wieslawsoltes/Perspex,SuperJMN/Avalonia,wieslawsoltes/Perspex,grokys/Perspex,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,jkoritzinsky/Perspex,AvaloniaUI/Avalonia,SuperJMN/Avalonia