Thanks for the tip.
I've just got some messages that showed on Debug area.
like this:
Oct 3 01:42:05 iOSPlayground-1 2015-10-03[2586] <Error>: CGContextSaveGState: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
Oct 3 01:42:05 iOSPlayground-1 2015-10-03[2586] <Error>: CGContextTranslateCTM: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
Oct 3 01:42:05 iOSPlayground-1 2015-10-03[2586] <Error>: CGContextRestoreGState: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.
any help?