update avalonia with critical fix.
MODIFY
Directory.Build.targets
Directory.Build.targets
<Project>
<PropertyGroup>
- <AvaloniaVersion>0.7.1-build1228-beta</AvaloniaVersion>
+ <AvaloniaVersion>0.7.1-build1248-beta</AvaloniaVersion>
<AvaloniaBehaviorsVersion>0.7.0</AvaloniaBehaviorsVersion>
</PropertyGroup>

MODIFY
WalletWasabi.Dependencies/AvalonStudio.Shell
WalletWasabi.Dependencies/AvalonStudio.Shell
-Subproject commit fc4adc0e613db27ef10d3e8668eec6c870f0919c
+Subproject commit 16a564e1891e43d8b688b483f4f2830b97ddf38e

update avalonia with critical fix.