hevc: check slice address length

It is used as get_bits argument and reading 0 bits isn't supported.
Reviewed-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>

libavcodec/hevc.c

@@ -459,7 +459,7 @@ static int hls_slice_header(HEVCContext *s)
 
         slice_address_length = av_ceil_log2(s->sps->ctb_width *
                                             s->sps->ctb_height);
-        sh->slice_segment_addr = get_bits(gb, slice_address_length);
+        sh->slice_segment_addr = slice_address_length ? get_bits(gb, slice_address_length) : 0;
         if (sh->slice_segment_addr >= s->sps->ctb_width * s->sps->ctb_height) {
             av_log(s->avctx, AV_LOG_ERROR,
                    "Invalid slice segment address: %u.\n",

libavcodec/hevc_parser.c

@@ -200,7 +200,7 @@ static inline int parse_nal_units(AVCodecParserContext *s, AVCodecContext *avctx
 
                 slice_address_length = av_ceil_log2_c(h->sps->ctb_width *
                                                       h->sps->ctb_height);
-                sh->slice_segment_addr = get_bits(gb, slice_address_length);
+                sh->slice_segment_addr = slice_address_length ? get_bits(gb, slice_address_length) : 0;
                 if (sh->slice_segment_addr >= h->sps->ctb_width * h->sps->ctb_height) {
                     av_log(h->avctx, AV_LOG_ERROR, "Invalid slice segment address: %u.\n",
                            sh->slice_segment_addr);