UIRefreshControl Crash App Parse.com Query - ios

Question

I have a UICollectionView with a UIRefreshControl. The UIRefreshControl runs a query to get objects from Parse.com. When I perform the refresh by "pulling down" it causes the app to crash and display this message:
fatal error: Cannot index empty buffer
However when I press a button or in the ViewDidLoad to run the same refresh code it does not crash and performs the query as required. Does this mean that there is something wrong with the dragging rather than the refresh code?
Here is the refresh code below (is it to do with the positioning of self.refreshControl.endRefreshing()?)
func refresh(sender:AnyObject)
{
println("Refresh")
self.orderedIdArray = []
self.idArray = []
self.organizerNameArray = []
self.categoryNameArray = []
self.classNameArray = []
var query = PFQuery(className:"Rides")
query.orderByAscending("date")
query.findObjectsInBackgroundWithBlock {
(objects: [AnyObject]!, error: NSError!) -> Void in
if error == nil {
// The find succeeded.
NSLog("Successfully retrieved \(objects.count) scores.")
// Do something with the found objects
for object in objects {
NSLog("%#", object.objectId)
var testId = object.objectId
println(testId)
self.orderedIdArray.append(testId)
var query = PFQuery(className:"Rides")
query.getObjectInBackgroundWithId(testId) {
(gameScore: PFObject!, error: NSError!) -> Void in
if error == nil {
NSLog("%#", gameScore)
//Gets the Values from Parse.com
self.organizerNameString = gameScore["organizer"] as String
self.categoryNameString = gameScore["category"] as String
self.classNameString = gameScore["class"] as String
self.organizerNameArray.append(self.organizerNameString)
self.categoryNameArray.append(self.categoryNameString)
self.classNameArray.append(self.classNameString)
self.idArray.append(object.objectId)
NSLog("%#", self.idArray)
} else {
println("Do not add to the array")
}
}
} else {
NSLog("%#", error)
}
self.collectionView?.reloadData()
}
}
} else {
// Log details of the failure
NSLog("Error: %# %#", error, error.userInfo!)
}
self.refreshControl.endRefreshing()
NSLog("Ordered: %#", self.orderedIdArray)
}
println("Completed the query")
}