fix: set workspaceFolders to null when there is no workspace

Based on  
https://microsoft.github.io/language-server-protocol/specifications/specification-current/#initialize

Author: aminya

lib/auto-languageclient.ts

@@ -123,7 +123,7 @@ export default class AutoLanguageClient {
       processId: process.pid,
       rootPath: projectPath,
       rootUri: Convert.pathToUri(projectPath),
-      workspaceFolders: [],
+      workspaceFolders: null,
       capabilities: {
         workspace: {
           applyEdit: true,