Added null handler check to getTags

Author: jkasten2

OneSignalSDK/app/src/test/java/com/test/onesignal/MainOneSignalClassRunner.java

@@ -754,6 +754,12 @@ public void testGetTagsWithNoTagsShouldBeNull() throws Exception {
       Assert.assertNull(lastGetTags);
    }
 
+   @Test
+   public void testGetTagNullCheck() throws Exception {
+      OneSignalInit();
+      OneSignal.getTags(null);
+   }
+
    @Test
    public void shouldGetTags() throws Exception {
       OneSignalInit();

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

@@ -734,6 +734,10 @@ public static void getTags(final GetTagsHandler getTagsHandler) {
          Log(LOG_LEVEL.ERROR, "You must initialize OneSignal before getting tags! Omitting this tag operation.");
          return;
       }
+      if (getTagsHandler == null) {
+         Log(LOG_LEVEL.ERROR, "getTagsHandler is null!");
+         return;
+      }
 
       JSONObject tags = OneSignalStateSynchronizer.getTags();
       if (tags == null || tags.toString().equals("{}"))