Assert nulls before setting user's details to local cache

app/src/main/java/chat/rocket/android/RocketChatCache.kt

@@ -408,7 +408,11 @@ object RocketChatCache {
         }, BackpressureStrategy.LATEST)
     }
 
-    fun setUserId(userId: String) = setString(KEY_USER_ID, userId)
+    fun setUserId(userId: String?) {
+        userId?.let {
+            setString(KEY_USER_ID, userId)
+        }
+    }
 
     fun getUserId(): String? = getString(KEY_USER_ID, null)
 
@@ -420,7 +424,11 @@ object RocketChatCache {
 
     fun getUserName(): String? = getString(KEY_USER_NAME, null)
 
-    fun setUserUsername(username: String) = setString(KEY_USER_USERNAME, username)
+    fun setUserUsername(username: String?) {
+        username?.let {
+            setString(KEY_USER_USERNAME, username)
+        }
+    }
 
     fun getUserUsername(): String? = getString(KEY_USER_USERNAME, null)
 }
\ No newline at end of file

app/src/main/java/chat/rocket/android/service/observer/CurrentUserObserver.java

@@ -20,68 +20,71 @@ import io.realm.RealmResults;
  * observe the user with emails.
  */
 public class CurrentUserObserver extends AbstractModelObserver<RealmUser> {
-  private final MethodCallHelper methodCall;
-  private boolean currentUserExists;
-  private ArrayList<Registrable> listeners;
+    private final MethodCallHelper methodCall;
+    private boolean currentUserExists;
+    private ArrayList<Registrable> listeners;
 
-  public CurrentUserObserver(Context context, String hostname,
-                             RealmHelper realmHelper) {
-    super(context, hostname, realmHelper);
-    methodCall = new MethodCallHelper(realmHelper);
-    currentUserExists = false;
-  }
+    public CurrentUserObserver(Context context, String hostname,
+                               RealmHelper realmHelper) {
+        super(context, hostname, realmHelper);
+        methodCall = new MethodCallHelper(realmHelper);
+        currentUserExists = false;
+    }
 
-  @Override
-  public RealmResults<RealmUser> queryItems(Realm realm) {
-    return RealmUser.queryCurrentUser(realm).findAll();
-  }
+    @Override
+    public RealmResults<RealmUser> queryItems(Realm realm) {
+        return RealmUser.queryCurrentUser(realm).findAll();
+    }
 
-  @Override
-  public void onUpdateResults(List<RealmUser> results) {
-    boolean exists = !results.isEmpty();
+    @Override
+    public void onUpdateResults(List<RealmUser> results) {
+        boolean exists = !results.isEmpty();
 
-    if (currentUserExists != exists) {
-      if (exists) {
-        onLogin(results.get(0));
-      } else {
-        onLogout();
-      }
-      currentUserExists = exists;
+        if (currentUserExists != exists) {
+            if (exists) {
+                onLogin(results.get(0));
+            } else {
+                onLogout();
+            }
+            currentUserExists = exists;
+        }
     }
-  }
 
-  @DebugLog
-  private void onLogin(RealmUser user) {
-    if (listeners != null) {
-      onLogout();
-    }
-    listeners = new ArrayList<>();
+    @DebugLog
+    private void onLogin(RealmUser user) {
+        if (listeners != null) {
+            onLogout();
+        }
+        listeners = new ArrayList<>();
 
-    RocketChatCache.INSTANCE.setUserId(user.getId());
-    RocketChatCache.INSTANCE.setUserUsername(user.getUsername());
-    RocketChatCache.INSTANCE.setUserName(user.getName());
+        String userId = user.getId();
+        String username = user.getUsername();
+        String name = user.getName();
 
-    final String userId = user.getId();
 
-    // get and observe Room subscriptions.
-    methodCall.getRoomSubscriptions().onSuccess(task -> {
-      if (listeners != null) {
-        Registrable listener = new StreamNotifyUserSubscriptionsChanged(
-            context, hostname, realmHelper, userId);
-        listener.register();
-        listeners.add(listener);
-      }
-      return null;
-    }).continueWith(new LogIfError());
-  }
+        RocketChatCache.INSTANCE.setUserId(userId);
+        RocketChatCache.INSTANCE.setUserUsername(username);
+        RocketChatCache.INSTANCE.setUserName(name);
+
+        // get and observe Room subscriptions.
+        methodCall.getRoomSubscriptions().onSuccess(task -> {
+            if (listeners != null) {
+                Registrable listener = new StreamNotifyUserSubscriptionsChanged(
+                        context, hostname, realmHelper, userId);
+                listener.register();
+                listeners.add(listener);
+            }
+            return null;
+        }).continueWith(new LogIfError());
+    }
 
-  @DebugLog
-  private void onLogout() {
-    if (listeners != null) {
-      for (Registrable listener : listeners) {
-        listener.unregister();
-      }
+    @DebugLog
+    private void onLogout() {
+        if (listeners != null) {
+            for (Registrable listener : listeners) {
+                listener.unregister();
+            }
+        }
+        listeners = null;
     }
-    listeners = null;
-  }
 }