DFA: fix "skip frame" TSW1 encoding.

Previously the decoder would raise an error.
The end result is the same, the time stamps only change
because regression tests create time stamps incorrectly.
Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>

libavcodec/dfa.c

@@ -67,6 +67,8 @@ static int decode_tsw1(uint8_t *frame, int width, int height,
 
     segments = bytestream_get_le32(&src);
     offset   = bytestream_get_le32(&src);
+    if (segments == 0 && offset == frame_end - frame)
+        return 0; // skip frame
     if (frame_end - frame <= offset)
         return -1;
     frame += offset;

tests/ref/fate/dfa4

-0, 0, 921600, 0xd9e060e3
-0, 12780, 921600, 0x15e28dc7
-0, 25560, 921600, 0x78e8bfbc
-0, 38340, 921600, 0xe9407075
-0, 51120, 921600, 0xab818b8a
+0, 0, 921600, 0x00000000
+0, 12780, 921600, 0xd9e060e3
+0, 25560, 921600, 0x15e28dc7
+0, 38340, 921600, 0x78e8bfbc
+0, 51120, 921600, 0xe9407075
 0, 63900, 921600, 0xab818b8a
 0, 76680, 921600, 0xab818b8a
 0, 89460, 921600, 0xab818b8a
 0, 102240, 921600, 0xab818b8a
 0, 115020, 921600, 0xab818b8a
-0, 127800, 921600, 0xad5ad11c
-0, 140580, 921600, 0xe6e50f8c
-0, 153360, 921600, 0x9f127099
+0, 127800, 921600, 0xab818b8a
+0, 140580, 921600, 0xad5ad11c
+0, 153360, 921600, 0xe6e50f8c
+0, 166140, 921600, 0x9f127099