lavc/h264_slice: drop redundant current_slice reset

It is done unconditionally in ff_h264_field_end()

libavcodec/h264_slice.c

@@ -1797,13 +1797,11 @@ int ff_h264_decode_slice_header(H264Context *h, H264SliceContext *sl,
 
             if (h->cur_pic_ptr && FIELD_PICTURE(h) && h->first_field) {
                 ret = ff_h264_field_end(h, h->slice_ctx, 1);
-                h->current_slice = 0;
                 if (ret < 0)
                     return ret;
             } else if (h->cur_pic_ptr && !FIELD_PICTURE(h) && !h->first_field && h->nal_unit_type  == H264_NAL_IDR_SLICE) {
                 av_log(h, AV_LOG_WARNING, "Broken frame packetizing\n");
                 ret = ff_h264_field_end(h, h->slice_ctx, 1);
-                h->current_slice = 0;
                 ff_thread_report_progress(&h->cur_pic_ptr->tf, INT_MAX, 0);
                 ff_thread_report_progress(&h->cur_pic_ptr->tf, INT_MAX, 1);
                 h->cur_pic_ptr = NULL;