fix NPE

Signed-off-by: tobiaskaminsky <tobias@kaminsky.me>

src/main/java/com/owncloud/android/authentication/AuthenticatorActivity.java

@@ -1704,15 +1704,20 @@ public class AuthenticatorActivity extends AccountAuthenticatorActivity
             // Reset webView
             webViewPassword = null;
             webViewUser = null;
+            forceOldLoginMethod = false;
             deleteCookies();
 
             if (success) {
                 finish();
             } else {
                 // init webView again
-                mLoginWebView.setVisibility(View.GONE);
+                if (mLoginWebView != null) {
+                    mLoginWebView.setVisibility(View.GONE);
+                }
                 setContentView(R.layout.account_setup);
 
+                initOverallUi();
+
                 CustomEditText serverAddressField = findViewById(R.id.hostUrlInput);
                 serverAddressField.setText(mServerInfo.mBaseUrl);