avcodec/jpeglsdec: Check for end of bitstream in ls_decode_line()

Fixes: 1773/clusterfuzz-testcase-minimized-4832523987189760

Fixes: Timeout

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit f80224ed19)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/jpeglsdec.c

@@ -233,6 +233,9 @@ static inline void ls_decode_line(JLSState *state, MJpegDecodeContext *s,
     while (x < w) {
         int err, pred;
 
+        if (get_bits_left(&s->gb) <= 0)
+            return;
+
         /* compute gradients */
         Ra = x ? R(dst, x - stride) : R(last, x);
         Rb = R(last, x);