avcodec/interplayvideo: use correct context when checking for enough bytes

Fixes #6502.
Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavcodec/interplayvideo.c

@@ -1044,7 +1044,7 @@ static void ipvideo_decode_format_10_opcodes(IpvideoContext *s, AVFrame *frame)
             for (x = 0; x < s->avctx->width; x += 8) {
                 s->pixel_ptr = s->cur_decode_frame->data[0] + x + y * s->cur_decode_frame->linesize[0];
 
-                while (skip <= 0 && bytestream2_get_bytes_left(&decoding_map_ptr) > 1)  {
+                while (skip <= 0 && bytestream2_get_bytes_left(&skip_map_ptr) > 1)  {
                     if (skip != -0x8000 && skip) {
                         opcode = bytestream2_get_le16(&decoding_map_ptr);
                         ipvideo_format_10_passes[pass](s, frame, opcode);