Parse.com prevent Cannot do a comparison query for type: (null)

Question

I would like to prevent the message "Cannot do a comparison query for type: (null)" I don't want to resolve it, because I know what's going wrong, but I would like to put exception. If Query doesn't find anything... NSLog something. (instead of crash)

Here is my code :

PFQuery *requestsToCurrentUser = [PFQuery queryWithClassName:@"FriendRequest"];
    [requestsToCurrentUser whereKey:@"to" equalTo:self.currentUser];
    [requestsToCurrentUser whereKey:@"status" equalTo:@"pending"];
    [requestsToCurrentUser findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {

        if (!error) {
            //this property stores the data for the tableView
            self.friendRequests = objects;
            //reload the table
            [self.tableView reloadData];

        } else {

            //error occcurred

        }
    }];

Answer 1

try to put this

if(!self.currentUser){
     // No value in self.currentUser
     return;
}
PFQuery *requestsToCurrentUser = [PFQuery queryWithClassName:@"FriendRequest"];
[requestsToCurrentUser whereKey:@"to" equalTo:self.currentUser];
[requestsToCurrentUser whereKey:@"status" equalTo:@"pending"];
[requestsToCurrentUser findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {

    if (!error) {
        //this property stores the data for the tableView
        self.friendRequests = objects;
        //reload the table
        [self.tableView reloadData];

    } else {

        //error occcurred

    }
}];