avcodec/hevc: Check entry point arrays for malloc failure

Fixes null pointer dereference
Fixes: signal_sigsegv_e1d3b6_2192_DBLK_F_VIXS_2.bit
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/hevc.c

@@ -654,6 +654,11 @@ static int hls_slice_header(HEVCContext *s)
             sh->entry_point_offset = av_malloc(sh->num_entry_point_offsets * sizeof(int));
             sh->offset = av_malloc(sh->num_entry_point_offsets * sizeof(int));
             sh->size = av_malloc(sh->num_entry_point_offsets * sizeof(int));
+            if (!sh->entry_point_offset || !sh->offset || !sh->size) {
+                sh->num_entry_point_offsets = 0;
+                av_log(s->avctx, AV_LOG_ERROR, "Failed to allocate memory\n");
+                return AVERROR(ENOMEM);
+            }
             for (i = 0; i < sh->num_entry_point_offsets; i++) {
                 int val = 0;
                 for (j = 0; j < segments; j++) {