avcodec/exr: Check remaining bits in last get code loop

Fixes: runtime error: shift exponent -7 is negative
Fixes: 3902/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_EXR_fuzzer-6081926122176512

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 dd8351b118)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/exr.c

@@ -558,7 +558,7 @@ static int huf_decode(const uint64_t *hcode, const HufDec *hdecod,
     while (lc > 0) {
         const HufDec pl = hdecod[(c << (HUF_DECBITS - lc)) & HUF_DECMASK];
 
-        if (pl.len) {
+        if (pl.len && lc >= pl.len) {
             lc -= pl.len;
             get_code(pl.lit, rlc, c, lc, gb, out, oe, outb);
         } else {