libvpx: Pull from upstream

source/libvpx/y4menc.c

 /*
  *  Copyright (c) 2014 The WebM project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 30 matching lines @@
       color = fmt == VPX_IMG_FMT_I44416 ? "C444p14 XYSCSS=444P14\n" :
               fmt == VPX_IMG_FMT_I42216 ? "C422p14 XYSCSS=422P14\n" :
               "C420p14 XYSCSS=420P14\n";
       break;
     case 16:
       color = fmt == VPX_IMG_FMT_I44416 ? "C444p16 XYSCSS=444P16\n" :
               fmt == VPX_IMG_FMT_I42216 ? "C422p16 XYSCSS=422P16\n" :
               "C420p16 XYSCSS=420P16\n";
       break;
     default:
+      color = NULL;
       assert(0);
   }
   return snprintf(buf, len, "YUV4MPEG2 W%u H%u F%u:%u I%c %s", width, height,
                   framerate->numerator, framerate->denominator, 'p', color);
 }
 
 int y4m_write_frame_header(char *buf, size_t len) {
   return snprintf(buf, len, "FRAME\n");
 }