Fix analyzer RCS1108 (#1469)

Author: josefpihrt

ChangeLog.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Fix analyzer [RCS1108](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1108) ([PR](https://github.com/dotnet/roslynator/pull/1469))
+
 ## [4.12.3] - 2024-05-10
 
 ### Fixed

src/Analyzers/CSharp/Analysis/AddStaticModifierToAllPartialClassDeclarationsAnalyzer.cs

@@ -54,11 +54,9 @@ private static void AnalyzeNamedType(SymbolAnalysisContext context)
 
         foreach (SyntaxReference syntaxReference in syntaxReferences)
         {
-            var classDeclaration = (ClassDeclarationSyntax)syntaxReference.GetSyntax(context.CancellationToken);
+            var classDeclaration = syntaxReference.GetSyntax(context.CancellationToken) as ClassDeclarationSyntax;
 
-            SyntaxTokenList modifiers = classDeclaration.Modifiers;
-
-            if (!modifiers.Contains(SyntaxKind.StaticKeyword))
+            if (classDeclaration?.Modifiers.Contains(SyntaxKind.StaticKeyword) == false)
             {
                 DiagnosticHelpers.ReportDiagnostic(
                     context,