Added null check

Author: marcarro

src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/CodeActions/Razor/ExtractToNewComponentCodeActionProvider.cs

@@ -128,6 +128,11 @@ private static bool IsInsideProperHtmlContent(RazorCodeActionContext context, Ma
         }
 
         var endOwner = syntaxTree.Root.FindInnermostNode(endLocation.Value.AbsoluteIndex, true);
+        
+        if (endOwner is null)
+        {
+            return null;
+        }
 
         // Correct selection to include the current node if the selection ends immediately after a closing tag.
         if (string.IsNullOrWhiteSpace(endOwner.ToFullString()) && endOwner.TryGetPreviousSibling(out var previousSibling))