Warning message in convert(., to = "stm") wrong

[AdaemmerP]

Describe the bug

convert(., to = "stm") correctly drops empty documents, but the warning message suggests that all documents are dropped.

Reproducible code

# documents with one empty document
docs <- c("",  
           "not empty",
           "also not empty")

# tokens -> dfm -> convert to stm format
docs |> 
  tokens() |> 
  dfm() |> 
  convert(to = "stm")


> Warning message:
> In dfm2stm(x, docvars, omit_empty = TRUE) : Dropped 3 empty document(s)

Expected behavior

The warning should state that 1 and not 3 empty documents are dropped.
It might even be better to throw an error so that the empty documents have to be dropped beforehand.

## System information

R version 4.3.2 (2023-10-31)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 22.04.3 LTS

Matrix products: default
BLAS:   /usr/lib/x86_64-linux-gnu/blas/libblas.so.3.10.0 
LAPACK: /usr/lib/x86_64-linux-gnu/lapack/liblapack.so.3.10.0

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

time zone: Europe/Berlin
tzcode source: system (glibc)

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

other attached packages:
[1] quanteda_3.3.1

Additional info

Please add any other information about the issue.

[AdaemmerP]

quanteda/R/convert.R

Line 320 in 06f424b

empty_docs <- rowSums(x) == 0

quanteda/R/convert.R

Line 323 in 06f424b

warning("Dropped ", format(length(empty_docs), big.mark = ","),

I assume length(empty_docs) has to be changed to sum(empty_docs)? If so the same holds for length(empty_feats) in line 328.