[Bug]: tm_outliers() without categorical variables doesn't generate good code

[llrs-roche]

What happened?

On the teal.gallery app under the exploratory app, the outlier module generates non reproducible code.

The error message generated is related to an issue on rtables (insightsengineering/rtables#1037) but the root cause is that the module generates an empty data.frame if there are no categorical variables this cannot be processed by rtables (and it doesn't make sense) .

A path to fix the issue is to not generate summary_data and try to print it with rtables if there is no categorical data.

Here is the app to reproduce this problem:

library(teal.modules.general)
library("teal.data")

## Data reproducible code ----
data <- within(teal_data(), {
  library("random.cdisc.data")
  ADSL <- radsl(seed = 1)
  ADRS <- radrs(ADSL, seed = 1)
  ADLB <- radlb(ADSL, seed = 1)
  ADLBPCA <- ADLB %>%
    dplyr::select(USUBJID, STUDYID, SEX, ARMCD, AVAL, AVISIT, PARAMCD) %>%
    tidyr::pivot_wider(
      values_from = "AVAL",
      names_from = c("PARAMCD", "AVISIT"),
      names_sep = " - "
    )
})

join_keys(data) <- default_cdisc_join_keys[c("ADSL", "ADRS", "ADLB", "ADLBPCA")]
ADLB <- data$ADLB

init(
  data = data,
  modules = modules(
    tm_outliers(
      "Outliers",
      outlier_var = data_extract_spec(
        dataname = "ADLB",
        select = select_spec(
          choices = variable_choices(ADLB, c("AVAL", "CHG", "PCHG", "BASE")),
          selected = "AVAL",
          multiple = FALSE,
          fixed = FALSE
        )
      ),
      categorical_var = data_extract_spec(
        dataname = "ADLB",
        select = select_spec(
          choices = variable_choices(ADLB, c("PARAM", "PARAMCD")),
          selected = NULL,
          multiple = FALSE,
          fixed = FALSE
        )
      )
    )
  )
) |> runApp()

The app will open but will crash when trying to add the card of the module on the report.
This is when code fails with an error message on the terminal:

sessionInfo()

Relevant log output

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[llrs-roche]

The proposal from Joe to fix this issue is to avoid generating the empty table with rtables (code from chevron):

rtables::rtable(
    header = "",
    rrow("", "Null Report: No observations met the reporting criteria for inclusion in this output."),
    inset = 2L
  )

This way way the table is present but it doesn't generate an error on the report construction.