avcodec/pthread_frame: Simplify code by using av_reallocp_array()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/pthread_frame.c

@@ -286,13 +286,10 @@ FF_ENABLE_DEPRECATION_WARNINGS
 
     if (src->slice_count && src->slice_offset) {
         if (dst->slice_count < src->slice_count) {
-            int *tmp = av_realloc(dst->slice_offset, src->slice_count *
+            int err = av_reallocp_array(&dst->slice_offset, src->slice_count,
                                         sizeof(*dst->slice_offset));
-            if (!tmp) {
-                av_free(dst->slice_offset);
-                return AVERROR(ENOMEM);
-            }
-            dst->slice_offset = tmp;
+            if (err < 0)
+                return err;
         }
         memcpy(dst->slice_offset, src->slice_offset,
                src->slice_count * sizeof(*dst->slice_offset));