[Navigation] Selection changed with null selecteditem triggers navigation

[nickrandolph]

Current behavior

From Commerce sample - selecting product triggers selection changed on Windows will null selecteditem, which is triggering navigation with a null item

Expected behavior

No navigation when no item selected

How to reproduce it (as minimally and precisely as possible)

Environment

Nuget Package:

Package Version(s):

Affected platform(s):

• iOS
• Android
• WebAssembly
• WebAssembly renders for Xamarin.Forms
• Windows
• Build tasks

Visual Studio:

• 2017 (version: )
• 2019 (version: )
• for Mac (version: )

Relevant plugins:

• Resharper (version: )

Anything else we need to know?