[Question]: (potential bug) variable names duplicated as "USUBJID.USUBJID" in "variable browser" module/tab (tm_variable_browser)

### What happened?

We developed a TEAL app, there seems variable name display issue (show as `.`) in "Variable Browser" module, variable name looks fine in other modules and in the filter panel, please see the screenshot below:

We did some processing for the ADSL (and other ADaM) dataset using `merge` and `left_join` function, but we checked data after the merging, it looks fine. In the TEAL app, the module code is as simple as below. We are wondering what could cause this issue or any potential bug in "tm_variable_browser()"?

```
modules = teal::modules(
teal.modules.general::tm_front_page(
header_text = c(
"Important information" = "This app should be used for exploratory use only."
),
show_metadata = TRUE
),

tm_data_table("Data Table"),
tm_variable_browser(label = "Variable browser"),
....
```


### sessionInfo()

```R
R version 4.3.1 (2023-06-16)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 22.04.3 LTS

Matrix products: default
BLAS/LAPACK: /usr/lib/x86_64-linux-gnu/openblas-pthread/libopenblasp-r0.3.20.so; LAPACK version 3.10.0

locale:
[1] LC_CTYPE=C.UTF-8 LC_NUMERIC=C LC_TIME=C.UTF-8
[4] LC_COLLATE=C.UTF-8 LC_MONETARY=C.UTF-8 LC_MESSAGES=C.UTF-8
[7] LC_PAPER=C.UTF-8 LC_NAME=C LC_ADDRESS=C
[10] LC_TELEPHONE=C LC_MEASUREMENT=C.UTF-8 LC_IDENTIFICATION=C

time zone: America/Los_Angeles
tzcode source: system (glibc)

attached base packages:
[1] stats graphics grDevices utils datasets methods base

other attached packages:
[1] tidyr_1.3.1 sparkline_2.0
[3] forcats_1.0.0 nestcolor_0.1.2
[5] rice_3.0.1 teal.reporter_0.3.1
[7] teal.connectors.rice_0.2.0 teal.modules.clinical_0.9.0
[9] tern_0.9.3 rtables_0.6.6
[11] magrittr_2.0.3 formatters_0.5.5
[13] teal.modules.general_0.3.0 teal.transform_0.5.0
[15] teal_0.15.2 teal.slice_0.5.0
[17] teal.data_0.5.0 teal.code_0.5.0
[19] ggmosaic_0.3.3 ggplot2_3.5.0
[21] dplyr_1.1.4 shiny_1.8.1

loaded via a namespace (and not attached):
[1] tidyselect_1.2.1 viridisLite_0.4.2 fastmap_1.1.1
[4] lazyeval_0.2.2 shinyjs_2.1.0 promises_1.2.1
[7] digest_0.6.35 estimability_1.5 mime_0.12
[10] tern.gee_0.1.3 lifecycle_1.0.4 survival_3.5-7
[13] compiler_4.3.1 ricepass_1.1.4 rlang_1.1.3
[16] sass_0.4.9 tools_4.3.1 utf8_1.2.4
[19] yaml_2.3.8 data.table_1.15.4 knitr_1.45
[22] htmlwidgets_1.6.4 curl_5.2.1 withr_3.0.0
[25] purrr_1.0.2 shinyWidgets_0.8.3 geepack_1.3.10
[28] grid_4.3.1 fansi_1.0.6 teal.logger_0.2.0
[31] xtable_1.8-4 colorspace_2.1-0 emmeans_1.10.0
[34] scales_1.3.0 MASS_7.3-60 cli_3.6.2
[37] mvtnorm_1.2-4 rmarkdown_2.26 generics_0.1.3
[40] tzdb_0.4.0 httr_1.4.7 cachem_1.0.8
[43] splines_4.3.1 assertthat_0.2.1 vctrs_0.6.5
[46] Matrix_1.6-1.1 jsonlite_1.8.8 hms_1.1.3
[49] ggrepel_0.9.5 crosstalk_1.2.1 teal.widgets_0.4.2
[52] fontawesome_0.5.2 plotly_4.10.4 jquerylib_0.1.4
[55] glue_1.7.0 DT_0.32 gtable_0.3.4
[58] later_1.3.2 shinycssloaders_1.0.0 munsell_0.5.0
[61] tibble_3.2.1 logger_0.3.0 pillar_1.9.0
[64] htmltools_0.5.8 R6_2.5.1 Rdpack_2.6
[67] evaluate_0.23 lattice_0.21-9 haven_2.5.4
[70] readr_2.1.5 rbibutils_2.2.16 backports_1.4.1
[73] memoise_2.0.1 broom_1.0.5 httpuv_1.6.15
[76] bslib_0.7.0 Rcpp_1.0.12 shinyvalidate_0.1.3
[79] nlme_3.1-163 checkmate_2.3.1 xfun_0.43
[82] fs_1.6.3 pkgconfig_2.0.3
```

### Relevant log output

_No response_

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