Fix warnings in external .NET projects

ExternalProjects/BizHawk.Analyzer/BizHawk.Analyzer.csproj

@@ -3,6 +3,9 @@
 		<TargetFramework>netstandard2.0</TargetFramework>
 	</PropertyGroup>
 	<Import Project="../../Common.props" />
+	<PropertyGroup>
+		<NoWarn>$(NoWarn);SA1200</NoWarn>
+	</PropertyGroup>
 	<ItemGroup>
 		<PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.2" PrivateAssets="all" />
 		<PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="3.8.0" PrivateAssets="all" />

ExternalProjects/BizHawk.SrcGen.ReflectionCache/ReflectionCacheGenerator.cs

@@ -31,7 +31,7 @@ namespace BizHawk.SrcGen.ReflectionCache
 			private string CalcNamespace()
 			{
 				// black magic wizardry to find common prefix https://stackoverflow.com/a/35081977
-				var ns = new string(_namespaces.First()
+				var ns = new string(_namespaces[0]
 					.Substring(0, _namespaces.Min(s => s.Length))
 					.TakeWhile((c, i) => _namespaces.All(s => s[i] == c))
 					.ToArray());
@@ -44,7 +44,7 @@ namespace BizHawk.SrcGen.ReflectionCache
 				{
 					SimpleNameSyntax simple => simple.Identifier.ValueText,
 					QualifiedNameSyntax qual => $"{Ser(qual.Left)}.{Ser(qual.Right)}",
-					_ => throw new Exception()
+					_ => throw new InvalidOperationException()
 				};
 				if (_namespace != null || syntaxNode is not NamespaceDeclarationSyntax syn) return;
 				var newNS = Ser(syn.Name);

ExternalProjects/iso-parser/ISOParser.csproj

@@ -3,4 +3,7 @@
 		<TargetFramework>netstandard2.0</TargetFramework>
 	</PropertyGroup>
 	<Import Project="../../Common.props" />
+	<PropertyGroup>
+		<Nullable>disable</Nullable>
+	</PropertyGroup>
 </Project>