Don't reset selection if source hasn't changed.
Don't reset selection if source hasn't changed.

Also remove some `?.` operators that aren't needed.

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