Move assertion to top of initializers.

Mobile Buy SDK/Mobile Buy SDK/Models/BUYApplePayToken.m

@@ -37,9 +37,10 @@
 
 - (instancetype)initWithPaymentToken:(PKPaymentToken *)paymentToken
 {
+	BUYAssert(paymentToken.paymentData.length > 0, @"Failed to initialize BUYApplePayToken. Invalid or nil paymentToken.");
+	
 	self = [super init];
 	if (self) {
-		BUYAssert(paymentToken.paymentData.length > 0, @"Failed to initialize BUYApplePayToken. Invalid or nil paymentToken.");
 		_paymentToken = paymentToken;
 	}
 	return self;

Mobile Buy SDK/Mobile Buy SDK/Models/BUYCreditCardToken.m

@@ -33,10 +33,10 @@
 
 - (instancetype)initWithPaymentSessionID:(NSString *)paymentSessionID
 {
+	BUYAssert(paymentSessionID.length > 0, @"Failed to initialize BUYCreditCardToken. Invalid or nil payment session ID.");
+	
 	self = [super init];
 	if (self) {
-		BUYAssert(paymentSessionID.length > 0, @"Failed to initialize BUYCreditCardToken. Invalid or nil payment session ID.");
-		
 		_paymentSessionID = paymentSessionID;
 	}
 	return self;