Fixes an iOS 9 crash with push notifications containing buttons

* With the new payload format, if a user selected an action on a push notification in iOS 9 the app would crash. This is because the payload format is different in iOS 9. Added a check for this condition to parse it appropriately

Author: Nightsd01

iOS_SDK/OneSignalSDK/Source/OSNotificationPayload.m

@@ -89,7 +89,14 @@ -(void)parseOSDataPayload {
     else {
         [self parseApnsFields];
         _attachments = os_data[@"att"];
-        [self parseActionButtons:os_data[@"buttons"]];
+        
+        // it appears that in iOS 9, the 'buttons' os_data field is an object not array
+        // this if statement checks for this condition and parses appropriately
+        if ([os_data[@"buttons"] isKindOfClass:[NSArray class]]) {
+            [self parseActionButtons:os_data[@"buttons"]];
+        } else if (os_data[@"buttons"] && [os_data[@"buttons"] isKindOfClass: [NSDictionary class]] && [os_data[@"buttons"][@"o"] isKindOfClass: [NSArray class]]) {
+            [self parseActionButtons:os_data[@"buttons"][@"o"]];
+        }
     }
 
     [self parseCommonOneSignalFields:_rawPayload[@"os_data"]];