Fixes after merge

Author: davidwengier

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Completion/DirectiveAttributeEventParameterCompletionItemProvider.cs

@@ -1,5 +1,5 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the MIT license. See License.txt in the project root for license information.
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections.Generic;
 using System.Collections.Immutable;

src/Razor/test/Microsoft.CodeAnalysis.Razor.Workspaces.Test/Completion/DirectiveAttributeEventParameterCompletionItemProviderTest.cs

@@ -1,5 +1,5 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the MIT license. See License.txt in the project root for license information.
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections.Generic;
 using Microsoft.AspNetCore.Razor.Language;
@@ -205,7 +205,7 @@ private static void AssertContains(IReadOnlyList<RazorCompletionItem> completion
     private RazorCompletionContext CreateRazorCompletionContext(TestCode documentContent)
     {
         var codeDocument = GetCodeDocument(documentContent.Text);
-        var syntaxTree = codeDocument.GetSyntaxTree();
+        var syntaxTree = codeDocument.GetRequiredSyntaxTree();
         var tagHelperDocumentContext = codeDocument.GetRequiredTagHelperContext();
         var absoluteIndex = documentContent.Position;