add failing test for issue #3155 add/remove grid child runtime throws exception
add failing test for issue #3155 add/remove grid child runtime throws exception

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