Cannot process empty grouped dataframes if process_md is TRUE

Prework

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Description

If one expects some Markdown in the column that contains the row groups, the current workaround is to set process_md to TRUE. If the dataframe is empty, this fails.

No issues with row names, or if process_md is FALSE.

Reproducible example

library(dplyr)
library(gt)

mtcars[0, ] |>
   gt::gt(
      groupname_col = "cyl",
      process_md = TRUE
   )
#> Error in `dplyr::recode()`:
#> ! No replacements provided.

mtcars[0, ] |>
   dplyr::group_by(cyl) |>
   gt::gt(
      process_md = TRUE
   )
#> Error in `dplyr::recode()`:
#> ! No replacements provided.

Expected result

An empty table.

No issues with row names or if Markdown processing is disabled:

mtcars[0, ] |>
   gt::gt(
      rowname_col = "cyl",
      process_md = TRUE
   )

mtcars[0, ] |>
   gt::gt(
      groupname_col = "cyl",
      process_md = FALSE
   )

mtcars[0, ] |>
   gt::gt(
      rowname_col = "cyl",
      process_md = FALSE
   )

These all produce an empty table:

Session info

Session info

sessionInfo()
#> R version 4.5.2 (2025-10-31 ucrt)
#> Platform: x86_64-w64-mingw32/x64
#> Running under: Windows 11 x64 (build 22631)
#> 
#> Matrix products: default
#>   LAPACK version 3.12.1
#> 
#> locale:
#> [1] LC_COLLATE=English_Switzerland.utf8  LC_CTYPE=English_Switzerland.utf8   
#> [3] LC_MONETARY=English_Switzerland.utf8 LC_NUMERIC=C                        
#> [5] LC_TIME=English_Switzerland.utf8    
#> 
#> time zone: Europe/Zurich
#> tzcode source: internal
#> 
#> attached base packages:
#> [1] stats     graphics  grDevices utils     datasets  methods   base     
#> 
#> other attached packages:
#> [1] gt_1.1.0    dplyr_1.1.4
#> 
#> loaded via a namespace (and not attached):
#>  [1] digest_0.6.38     R6_2.6.1          fastmap_1.2.0     tidyselect_1.2.1 
#>  [5] xfun_0.54         magrittr_2.0.4    glue_1.8.0        tibble_3.3.0     
#>  [9] knitr_1.50        pkgconfig_2.0.3   htmltools_0.5.8.1 generics_0.1.4   
#> [13] rmarkdown_2.30    lifecycle_1.0.4   xml2_1.4.1        cli_3.6.5        
#> [17] vctrs_0.6.5       reprex_2.1.1      withr_3.0.2       compiler_4.5.2   
#> [21] tools_4.5.2       pillar_1.11.1     evaluate_1.0.5    yaml_2.3.10      
#> [25] rlang_1.1.6       fs_1.6.6