[Rendering] Bug Title Here

[beervoley]

Target Platforms

UWP

SDK Version

10.0.17763.0

Application Name

N/A

Problem Description

We need to check RootElement for nullptr here https://github.com/microsoft/AdaptiveCards/blob/4745cb65ae8d57529811f7a0ba13f04afbadcacc/source/uwp/SharedRenderer/lib/XamlBuilder.cpp#L58 to avoid various crashes (AV most common) if we failed to render rootelement.

Screenshots

No response

Card JSON

[]

Sample Code Language

No response

Sample Code

No response