Fix error code

[Koze]

Type of instance

Type of code property of NSError is NSInteger.

@property(readonly) NSInteger code

So I changed type NSUInteger to NSInteger.

64bit support

String format for NSIntegerand NSUInteger needs cast for fixing warning.

Reference is in the following. https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/Strings/Articles/formatSpecifiers.html#//apple_ref/doc/uid/TP40004265-SW5