The assert that cached value of config file existance is always corre…

…ct, might not be true if file watcher is not invoked before creating configured project

src/server/editorServices.ts

@@ -1234,7 +1234,8 @@ namespace ts.server {
         private setConfigFileExistenceByNewConfiguredProject(project: ConfiguredProject) {
             const configFileExistenceInfo = this.getConfigFileExistenceInfo(project);
             if (configFileExistenceInfo) {
-                Debug.assert(configFileExistenceInfo.exists);
+                // The existance might not be set if the file watcher is not invoked by the time config project is created by external project
+                configFileExistenceInfo.exists = true;
                 // close existing watcher
                 if (configFileExistenceInfo.configFileWatcherForRootOfInferredProject) {
                     const configFileName = project.getConfigFilePath();