avoid null value error

Author: Niall Brennan

src/main/java/com/segment/analytics/android/integrations/firebase/FirebaseIntegration.java

@@ -26,6 +26,7 @@
 
 import static com.segment.analytics.internal.Utils.hasPermission;
 import static com.segment.analytics.internal.Utils.isNullOrEmpty;
+import static java.util.Objects.isNull;
 
 /**
  * Google Analytics for Firebase is a free app measurement solution that provides insight on app
@@ -211,7 +212,7 @@ && isNullOrEmpty(properties.currency())) {
       } else {
         property = makeKey(property);
       }
-      if (property.equals(Param.ITEMS)) {
+      if (property.equals(Param.ITEMS) && value != null) {
         List<ValueMap> products = properties.getList("products", ValueMap.class);
         ArrayList<Bundle> mappedProducts = formatProducts(products);
         bundle.putParcelableArrayList(property, mappedProducts);

src/test/java/com/segment/analytics/android/integration/firebase/FirebaseTest.java

@@ -152,6 +152,23 @@ public void trackPurchaseWithProducts() {
         verify(firebase).logEvent(eq("purchase"), bundleEq(expected));
     }
 
+    @Test
+    public void trackPurchaseWithNullProducts() {
+        Properties properties = new Properties()
+                .putValue("revenue", 100.0)
+                .putValue("currency", "USD")
+                .putValue("products", null);
+
+        integration.track(new TrackPayload.Builder().anonymousId("1234").properties(properties).event("Order Completed").build());
+
+        Bundle expected = new Bundle();
+        expected.putDouble("value", 100.0);
+        expected.putString("currency", "USD");
+        expected.putString("items", null);
+
+        verify(firebase).logEvent(eq("purchase"), bundleEq(expected));
+    }
+
     @Test
     public void trackWithEventNameTransformation() {
         Properties properties = new Properties()