Replaced hard-coded indexer with its actual name
Replaced hard-coded indexer with its actual name

This was possibly just overlooked since nobody probably ever changed the name from "Item".
AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia