fix(vscode): catch one more undefined tsconfig case (#2459)

Author: MaxKless

libs/vscode/typescript-plugin/src/lib/plugin-configuration.ts

@@ -45,6 +45,9 @@ async function getAdditionalRootFiles(
   if (!('compilerOptions' in tsconfig)) {
     tsconfig = (await readAndCacheJsonFile('tsconfig.json', workspaceRoot))
       .json;
+    if (!tsconfig) {
+      return [];
+    }
     if (!('compilerOptions' in tsconfig)) {
       return [];
     }