'java.lang.String com.dropbox.core.DbxRequestConfig.getUserLocale()' on a null object reference

Login with dropbox account I got crash.
implementation 'com.dropbox.core:dropbox-core-sdk:4.0.1'
Api level 30

My Code :

`public class DbxRequestConfigFactory {`
` private static DbxRequestConfig sDbxRequestConfig;`
` public static DbxRequestConfig getRequestConfig() {`
` if (sDbxRequestConfig == null) {`
` sDbxRequestConfig = DbxRequestConfig.newBuilder("myapp-dropbox-v2")`
` .withHttpRequestor(new OkHttp3Requestor(OkHttp3Requestor.defaultOkHttpClient()))`
` .build();`
` }`
` return sDbxRequestConfig;`
`}`
`}`

`Auth.startOAuth2PKCE(this, getString(R.string.app_key),DbxRequestConfigFactory.getRequestConfig());`

Logs below

Fatal Exception: java.lang.RuntimeException: An error occurred while executing doInBackground()
at android.os.AsyncTask$4.done(AsyncTask.java:399)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
at java.util.concurrent.FutureTask.run(FutureTask.java:271)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:289)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:919)

Caused by java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.dropbox.core.DbxRequestConfig.getUserLocale()' on a null object reference
at com.dropbox.core.DbxPKCEManager.makeTokenRequest(DbxPKCEManager.java:107)
at com.dropbox.core.android.AuthActivity$TokenRequestAsyncTask.doInBackground(AuthActivity.java:793)
at com.dropbox.core.android.AuthActivity$TokenRequestAsyncTask.doInBackground(AuthActivity.java:782)
at android.os.AsyncTask$3.call(AsyncTask.java:378)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:289)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:919)