Add missing PIX_FMT_NONE to libopenjpegenc

fixes ticket #813

Reviewed-by: Michael Niedermayer <michaelni@gmx.at>
Reviewed-by: Jean First <jeanfirst@gmail.com>
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit ef611095f0)

libavcodec/libopenjpegenc.c

@@ -372,6 +372,7 @@ AVCodec ff_libopenjpeg_encoder = {
                                            PIX_FMT_YUV440P,PIX_FMT_YUV444P,
                                            PIX_FMT_YUV420P9,PIX_FMT_YUV422P9,PIX_FMT_YUV444P9,
                                            PIX_FMT_YUV420P10,PIX_FMT_YUV422P10,PIX_FMT_YUV444P10,
-                                           PIX_FMT_YUV420P16,PIX_FMT_YUV422P16,PIX_FMT_YUV444P16},
+                                           PIX_FMT_YUV420P16,PIX_FMT_YUV422P16,PIX_FMT_YUV444P16,
+                                           PIX_FMT_NONE},
     .long_name = NULL_IF_CONFIG_SMALL("OpenJPEG based JPEG 2000 encoder"),
 } ;