How to use a function that displays a Sankey diagram in a flexdashboard with a runtime: shiny?

Hello, I would like to make a Sankey diagram in a dynamic Dashboard.
I have two tables that are stored in a list (libs)

For that, I have created a function that allows me to do that. But when I put the function in a highcharter::renderHighchart, I get the error message "
Error in UseMethod: no method for 'rename' applicable for an object of class "NULL"

---
title: "Dashboard d'analyse Profilx"
output: 
  flexdashboard::flex_dashboard:
    orientation: columns
    vertical_layout: fill
    theme:
      bg: "#fcfcfc"
      fg: "#8e868f"
      primary: "#008CBA"
      font_scale: 0.85
      base_font: !expr bslib::font_google("Prompt")
      code_font: !expr bslib::font_google("JetBrains Mono")
    source_code: embed

runtime: shiny
---


```{r setup, include=FALSE}
library(dplyr)
library(purrr)
library(data.table)
library(flexdashboard)
library(highcharter)
library(featurize)
library(DT)
library(stringi)
library(stringr)
library(glue)
library(ggplot2)
library(grid)
library(tidyr)
library(plotly)
library(readxl)
library(readr)
library(reactable)
library(billboarder)
library(shiny)
library(scales)
library(shinyWidgets)
library(bsts)
library(viridis)
library(bslib)
library(aws.s3)
library(profvis)

  
thematic::thematic_rmd(
  font = "auto",
  # To get the dark bg on the geom_raster()
  sequential = thematic::sequential_gradient(fg_low = FALSE, fg_weight = 0, bg_weight = 1)
)
theme_set(theme_bw(base_size = 20))

Sys.setenv("aws_access_key_id" = "",
           "aws_secret_access_key" = "",
           "aws_region" = "eu-west-1",
           "aws_default_region" = "eu-west-1",
           "aws_session_token" = "")



list = aws.s3::get_bucket_df("cdh-dsdevmodels-382109",
                      prefix = "profilxmodels/stage=all") %>%
pull(Key)

version <- list %>% 
  gsub(".*version=(.+)/model.*", "\\1",.)

lib_files <- setNames(list, version)

libs <- purrr::map(lib_files, ~s3readRDS(object = .x, bucket = "cdh-dsdevmodels-382109"))

Version {.sidebar}

selectInput(inputId = "lib_version", 
            label = "Selectionner une version :",
            choices = lib_files)

selectInput(inputId = "segment_type", 
            label = "Selectionner un segment :",
            choices = c("C3_C4","C2"),
            selected = "C3_C4")

selectInput(inputId = "Niveau",
            label = "Selectionner le niveau :",
            choices = 1:5)

version_actual <- reactive({
  req(input$lib_version)
  gsub(".*version=(.+)/model.*", "\\1", input$lib_version)
  
})
  

bib <- reactive({
  req(input$lib_version, version_actual())
  x <- libs[[version_actual()]]
  if (version_actual() == "0.1.0") {
    l <- list()
    l$tlp_lib <- list()
    l$model <- list()
    
    l$tlp_lib$C3_C4 <- x$tlp_lib
    l$tlp_lib$C2 <- NULL
    
    l$model$C2 <- NULL
    l$model$C3_C4 <- x$model
    l$model$C3_C4$pre$actions$recipe$recipe$template <- l$model$C3_C4$pre$actions$recipe$recipe$template %>%
     rename(CLUST = CLUST6)
    x <- l
  }
  x
})

observe({

  if(is.null(bib()$tlp_lib$C2)) {
    updateSelectInput(session, inputId = "segment_type", choices = "C3_C4")
  } else{
    updateSelectInput(session, inputId = "segment_type", choices = c("C3_C4","C2"))
  }
})

# The fonction 
sankey_function <- function(old_clust, new_clust,  version_to_compare) {
  new_clust <- rename(new_clust, new := CLUST)
  old_clust <- rename(old_clust, old := CLUST)
  
  df <- inner_join(old_clust, new_clust) %>%
    group_by(new, old) %>%
    summarise(nb_mp_code = n()) %>%
    mutate(new := paste0(as.character(version_to_compare), ' : ', new),
           old := paste0(as.character(version_actual()), ' : ', old))
  
  hchart(df, "sankey", hcaes(from = old, to = new, weight = nb_mp_code)) %>%
    hc_boost(enabled = TRUE)
}

highcharter::renderHighchart({
  req(bib())
  version[!version %in% c(version_actual())] %>%
    purrr::map(
      ~ sankey_function(
        libs[[.x]]$model$C3_C4$pre$actions$recipe$recipe$template,
        bib()$model$C3_C4$pre$actions$recipe$recipe$template,
.x
      )
    )
})