SSL pinning with AFNetworking crash issue

Question

I wanna do SSL pinning for my app with AFNetworking. Below is my code.

    NSString *certificatePath = [[NSBundle mainBundle] pathForResource:@"fileName" ofType:@"crt"];
    NSData *data = [NSData dataWithContentsOfFile:certificatePath];
    NSSet *set = [NSSet setWithObjects:data, nil];
    AFSecurityPolicy *securityPolicy = [AFSecurityPolicy policyWithPinningMode:AFSSLPinningModeCertificate];
    [securityPolicy setValidatesDomainName:NO];
    [securityPolicy setAllowInvalidCertificates:YES];
    [securityPolicy setPinnedCertificates:set];
    requestManager.securityPolicy = securityPolicy;

But app is crashing with above code with this error *** -[__NSArrayM insertObject:atIndex:]: object cannot be nil'

When I change the pinning mode to AFSSLPinningModePublicKey, its crashing with different error "The certificate for this server is invalid. You might be connecting to a server that is pretending to be “Domain name” which could put your confidential information at risk." Not sure what could be the issue.