Fix completion handler bug that causes language server to crash (#7401)

filter out incorrect request, can be undone after issue # 7250 is resolved

Author: Jordi Ramos

src/razor/src/completion/completionHandler.ts

@@ -156,7 +156,10 @@ export class CompletionHandler {
         // TODO: Snippet support
 
         try {
-            if (delegatedCompletionItemResolveParams.originatingKind != LanguageKind.CSharp) {
+            if (
+                delegatedCompletionItemResolveParams.originatingKind != LanguageKind.CSharp ||
+                delegatedCompletionItemResolveParams.completionItem.data.TextDocument == null
+            ) {
                 return delegatedCompletionItemResolveParams.completionItem;
             } else {
                 const newItem = await vscode.commands.executeCommand<CompletionItem>(