avcodec/loco: Check for end of input in the first line

Fixes: Timeout (85sec -> 0.1sec)
Fixes: 17634/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_LOCO_fuzzer-5666410809786368

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

libavcodec/loco.c

@@ -155,6 +155,8 @@ static int loco_decode_plane(LOCOContext *l, uint8_t *data, int width, int heigh
     /* restore top line */
     for (i = 1; i < width; i++) {
         val = loco_get_rice(&rc);
+        if (val == INT_MIN)
+           return AVERROR_INVALIDDATA;
         data[i] = data[i - 1] + val;
     }
     data += stride;