delete_part 输出pdf时删除上边框

如何解决delete_part 输出pdf时删除上边框

我正在使用以下 rmarkdown 代码，使用 xelatex 引擎：

access <- function(x,...) {
  x <- delete_part(x)
  x <- colformat_double(x,big.mark = "'",decimal.mark = ",")
  x <- set_table_properties(x,layout = "autofit")
  x <- border_remove(x)
  std_border <- fp_border_default(width = 1,color = "black")
  x <- border_outer(x,part="all",border = std_border )
  x <- border_inner_h(x,border = std_border,part="all")
  x <- border_inner_v(x,part="all")
  autofit(x)
}

firstc <- c("Field:","Table:","Sort:","Show:","Criteria:","Or:")
secondc <- c("Field:","Or:")
```

```{r echo=FALSE}
tabela <- data.frame(firstc,secondc)
ft <- flextable(tabela)
ft <- access(ft)
ft <- hline_top(ft)

ft <- fit_to_width(ft,max_width = 4)
ft <- set_table_properties(ft,layout = "autofit",width = 1)
ft
```

但是，顶部的 hline 没有显示在 PDF 输出中。

有什么想法吗？