See the example below I'm using the latest dev version of data.table on Windows.
library(data.table)
x <- data.table(A = character(), B = double())
x[, A := ordered(A, levels = character())]
rbind(x, x)
#> Error in rbindlist(l, use.names, fill, idcol): STRING_PTR() can only be applied to a 'character', not a 'NULL'
rbind(x, x)
#> Error in rbindlist(l, use.names, fill, idcol): Internal error: savetl_init checks failed (0 100 0x0000000021484990 0x000000001f6b7530). please report to data.table issue tracker.
Created on 2020-11-03 by the reprex package (v0.3.0)
Session info
devtools::session_info()
#> - Session info ---------------------------------------------------------------
#> setting value
#> version R version 4.0.2 (2020-06-22)
#> os Windows 10 x64
#> system x86_64, mingw32
#> ui RTerm
#> language en
#> collate Chinese (Simplified)_China.936
#> ctype Chinese (Simplified)_China.936
#> tz Asia/Taipei
#> date 2020-11-03
#>
#> - Packages -------------------------------------------------------------------
#> package * version date lib source
#> assertthat 0.2.1 2019-03-21 [2] CRAN (R 4.0.0)
#> backports 1.1.7 2020-05-13 [2] CRAN (R 4.0.0)
#> callr 3.4.3 2020-03-28 [2] CRAN (R 4.0.0)
#> cli 2.0.2 2020-02-28 [2] CRAN (R 4.0.0)
#> crayon 1.3.4 2017-09-16 [2] CRAN (R 4.0.0)
#> data.table * 1.13.3 2020-11-03 [1] local
#> desc 1.2.0 2018-05-01 [2] CRAN (R 4.0.0)
#> devtools 2.3.0 2020-04-10 [2] CRAN (R 4.0.0)
#> digest 0.6.25 2020-02-23 [2] CRAN (R 4.0.0)
#> ellipsis 0.3.1 2020-05-15 [2] CRAN (R 4.0.2)
#> evaluate 0.14 2019-05-28 [2] CRAN (R 4.0.0)
#> fansi 0.4.1 2020-01-08 [2] CRAN (R 4.0.0)
#> fs 1.5.0 2020-07-31 [2] CRAN (R 4.0.2)
#> glue 1.4.2 2020-08-27 [2] CRAN (R 4.0.2)
#> highr 0.8 2019-03-20 [2] CRAN (R 4.0.0)
#> htmltools 0.5.0 2020-06-16 [2] CRAN (R 4.0.0)
#> knitr 1.29 2020-06-23 [2] CRAN (R 4.0.0)
#> magrittr 1.5 2014-11-22 [2] CRAN (R 4.0.0)
#> memoise 1.1.0 2017-04-21 [2] CRAN (R 4.0.0)
#> pkgbuild 1.0.7 2020-04-25 [2] CRAN (R 4.0.0)
#> pkgload 1.0.2 2018-10-29 [2] CRAN (R 4.0.0)
#> prettyunits 1.1.1 2020-01-24 [2] CRAN (R 4.0.0)
#> processx 3.4.3 2020-07-05 [2] CRAN (R 4.0.2)
#> ps 1.3.4 2020-08-11 [2] CRAN (R 4.0.2)
#> R6 2.4.1 2019-11-12 [2] CRAN (R 4.0.0)
#> remotes 2.2.0 2020-07-21 [2] CRAN (R 4.0.2)
#> rlang 0.4.7 2020-07-09 [2] CRAN (R 4.0.2)
#> rmarkdown 2.4 2020-09-30 [2] CRAN (R 4.0.2)
#> rprojroot 1.3-2 2018-01-03 [2] CRAN (R 4.0.0)
#> sessioninfo 1.1.1 2018-11-05 [2] CRAN (R 4.0.0)
#> stringi 1.4.6 2020-02-17 [2] CRAN (R 4.0.0)
#> stringr 1.4.0 2019-02-10 [2] CRAN (R 4.0.0)
#> testthat 2.3.2.9000 2020-05-09 [2] local
#> usethis 1.6.1 2020-04-29 [2] CRAN (R 4.0.0)
#> withr 2.2.0 2020-04-20 [2] CRAN (R 4.0.0)
#> xfun 0.18 2020-09-29 [2] CRAN (R 4.0.2)
#> yaml 2.2.1 2020-02-01 [2] CRAN (R 4.0.0)
#>
#> [1] D:/R/R-dev
#> [2] D:/app/R_lib/4.0
#> [3] D:/app/R-4.0.0/library
See the example below I'm using the latest dev version of data.table on Windows.
Created on 2020-11-03 by the reprex package (v0.3.0)
Session info