Fix IAM preview message id NPE

* messageDisplayQueue.contains was returning NPE in a preview case, due to message id being null
* message can be null if preview display fails
* Add message null check and preview check

Author: Jeasmine

OneSignalSDK/onesignal/src/main/java/com/onesignal/OSInAppMessageController.java

@@ -612,8 +612,8 @@ private void dismissCurrentMessage(@Nullable OSInAppMessage message) {
 
         inAppMessageShowing = false;
         synchronized (messageDisplayQueue) {
-            if (messageDisplayQueue.size() > 0) {
-                if (message != null && !messageDisplayQueue.contains(message)) {
+            if (message != null && !message.isPreview && messageDisplayQueue.size() > 0) {
+                if (!messageDisplayQueue.contains(message)) {
                     OneSignal.onesignalLog(OneSignal.LOG_LEVEL.DEBUG, "Message already removed from the queue!");
                     return;
                 } else {