When getuser() failed, the app will crash

[Android-Login-Analysis]

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.meisolsson.githubsdk.model.User.login()' on a null object reference
at com.github.pockethub.android.accounts.LoginActivity.endAuth(LoginActivity.java:78)
at com.github.pockethub.android.accounts.LoginActivity.lambda$onUserLoggedIn$1(LoginActivity.java:45)

The reason is when userService.getUser() is null, user.login will crash.