Fix for a crash in logout (closes #263) (#303)

* Fix for ActivityNotFoundException (closes #166)

* Change RESULT_OK to RESULT_CANCELED

* Fix crash in logout

* Test for a case when FragmentManager is destroyed

* Revert "Test for a case when FragmentManager is destroyed"

This reverts commit 1dfebb0.

library/src/main/java/com/okta/oidc/OktaResultFragment.java

@@ -22,6 +22,7 @@
 import androidx.annotation.RestrictTo;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentActivity;
+import androidx.fragment.app.FragmentManager;
 
 import com.okta.oidc.net.request.web.WebRequest;
 
@@ -58,10 +59,12 @@ public static void addLogoutFragment(WebRequest request,
         OktaResultFragment fragment = new OktaResultFragment();
         fragment.logoutIntent = createAuthIntent(activity, request.toUri(), customTabOptions,
                 browsers);
-        activity.getSupportFragmentManager()
-                .beginTransaction()
-                .add(fragment, AUTHENTICATION_REQUEST)
-                .commit();
+        FragmentManager fragmentManager = activity.getSupportFragmentManager();
+        if (!fragmentManager.isDestroyed()) {
+            fragmentManager.beginTransaction()
+                           .add(fragment, AUTHENTICATION_REQUEST)
+                           .commit();
+        }
     }
 
     @Override