ArgumentNullException on multiple tfms

[rgroenewoudt]

ArgumentNullException happens when parsing a project containing < TargetFrameworks >

Stacktrace:

>	NuGet.Frameworks.dll!NuGet.Frameworks.NuGetFramework.Parse(string folderName, NuGet.Frameworks.IFrameworkNameProvider mappings) Line 377	C#
 	Snitch.dll!Snitch.Analysis.AnalyzerResultExtensions.GetNearestFrameworkMoniker.AnonymousMethod__0(string x) Line 28	C#
 	System.Linq.dll!System.Linq.Enumerable.ToDictionary<string, NuGet.Frameworks.NuGetFramework, string>(System.Collections.Generic.IEnumerable<string> source, System.Func<string, NuGet.Frameworks.NuGetFramework> keySelector, System.Func<string, string> elementSelector, System.Collections.Generic.IEqualityComparer<NuGet.Frameworks.NuGetFramework> comparer) Line 8144	C#
 	Snitch.dll!Snitch.Analysis.AnalyzerResultExtensions.GetNearestFrameworkMoniker(NuGet.Frameworks.NuGetFramework framework, System.Collections.Generic.IEnumerable<string> candidates) Line 26	C#
 	Snitch.dll!Snitch.Analysis.AnalyzerResultExtensions.GetNearestFrameworkMoniker(System.Collections.Generic.IEnumerable<Buildalyzer.IAnalyzerResult> source, string framework) Line 18	C#
 	Snitch.dll!Snitch.Analysis.ProjectBuilder.Build(Buildalyzer.AnalyzerManager manager, Snitch.Analysis.Project project, string tfm, int indentation) Line 166	C#

Project.TargetFramework and IAnalyzerResult.TargetFramework are null, which causes issues.

Example csproj:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
	<TargetFrameworks>net48;net8.0</TargetFrameworks>
  </PropertyGroup>

</Project>