check(set-avatar): user id

Signed-off-by: alperozturk96 <alper_ozturk@proton.me>

Author: alperozturk96

app/src/main/java/com/owncloud/android/utils/DisplayUtils.java

@@ -434,6 +434,11 @@ public static void setAvatar(@NonNull User user, AvatarGenerationListener listen
         String userId = accountManager.getUserData(user.toPlatformAccount(),
                 com.owncloud.android.lib.common.accounts.AccountUtils.Constants.KEY_USER_ID);
 
+        if (userId == null) {
+            Log_OC.e(TAG, "user id is null, cannot set avatar");
+            return;
+        }
+
         setAvatar(user, userId, listener, avatarRadius, resources, callContext, context);
     }