Fixed bug in Grid.
Fixed bug in Grid.

Bug came from Moonlight. Fixes #3.

SuperJMN/Avalonia,jkoritzinsky/Avalonia,OronDF343/Avalonia,susloparovdenis/Avalonia,jkoritzinsky/Avalonia,danwalmsley/Perspex,AvaloniaUI/Avalonia,wieslawsoltes/Perspex,kekekeks/Perspex,SuperJMN/Avalonia,punker76/Perspex,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,Perspex/Perspex,grokys/Perspex,AvaloniaUI/Avalonia,susloparovdenis/Avalonia,akrisiun/Perspex,SuperJMN/Avalonia,susloparovdenis/Perspex,AvaloniaUI/Avalonia,ncarrillo/Perspex,MrDaedra/Avalonia,jkoritzinsky/Avalonia,DavidKarlas/Perspex,AvaloniaUI/Avalonia,wieslawsoltes/Perspex,SuperJMN/Avalonia,wieslawsoltes/Perspex,kekekeks/Perspex,SuperJMN/Avalonia,jazzay/Perspex,jkoritzinsky/Avalonia,AvaloniaUI/Avalonia,tshcherban/Perspex,wieslawsoltes/Perspex,susloparovdenis/Perspex,sagamors/Perspex,Perspex/Perspex,jkoritzinsky/Perspex,SuperJMN/Avalonia,OronDF343/Avalonia,bbqchickenrobot/Perspex,AvaloniaUI/Avalonia,SuperJMN/Avalonia,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,MrDaedra/Avalonia,AvaloniaUI/Avalonia,wieslawsoltes/Perspex,grokys/Perspex,wieslawsoltes/Perspex