avcodec/ffv1dec_template: Check for the end of input after 1024 pixels

Fixes: Timeout
Fixes: 10385/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_FFV1_fuzzer-5689206987292672

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/ffv1dec_template.c

@@ -50,6 +50,11 @@ static av_always_inline int RENAME(decode_line)(FFV1Context *s, int w,
     for (x = 0; x < w; x++) {
         int diff, context, sign;
 
+        if (!(x & 1023)) {
+            if (is_input_end(s))
+                return AVERROR_INVALIDDATA;
+        }
+
         context = RENAME(get_context)(p, sample[1] + x, sample[0] + x, sample[1] + x);
         if (context < 0) {
             context = -context;