Fixed NRE in SystemDialogImpl
Fixed NRE in SystemDialogImpl

susloparovdenis/Avalonia,grokys/Perspex,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,OronDF343/Avalonia,jkoritzinsky/Perspex,SuperJMN/Avalonia,wieslawsoltes/Perspex,jkoritzinsky/Avalonia,susloparovdenis/Avalonia,jkoritzinsky/Avalonia,punker76/Perspex,AvaloniaUI/Avalonia,akrisiun/Perspex,AvaloniaUI/Avalonia,OronDF343/Avalonia,jkoritzinsky/Avalonia,susloparovdenis/Perspex,jkoritzinsky/Avalonia,susloparovdenis/Perspex,SuperJMN/Avalonia,AvaloniaUI/Avalonia,SuperJMN/Avalonia,SuperJMN/Avalonia,wieslawsoltes/Perspex,wieslawsoltes/Perspex,grokys/Perspex,jkoritzinsky/Avalonia,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,MrDaedra/Avalonia,SuperJMN/Avalonia,Perspex/Perspex,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,MrDaedra/Avalonia,wieslawsoltes/Perspex,wieslawsoltes/Perspex,Perspex/Perspex,jazzay/Perspex,SuperJMN/Avalonia,SuperJMN/Avalonia,wieslawsoltes/Perspex