`makeXFunction`s does not throw correct error message if argument is missing

[tdeenes]

makeAssertionFunction() and makeExpectationFunction() return empty character instead of the argument name if the argument is missing.

library(checkmate)
printErrMsg = function(expr) tryCatch(expr, error = function(e) print(conditionMessage(e)))
checkInt() |> printErrMsg()
# [1] "argument \"x\" is missing, with no default"
testInt() |> printErrMsg()
# [1] "argument \"x\" is missing, with no default"
assertInt() |> printErrMsg()
# [1] "argument \"\" is missing, with no default"
expect_int() |> printErrMsg()
[1] "Argument '' is missing"

[tdeenes]

Session info:

> sessionInfo()
R version 4.5.1 (2025-06-13)
Platform: x86_64-pc-linux-gnu
Running under: Linux Mint 21

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  LAPACK version 3.10.0

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8    
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8   
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

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

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

other attached packages:
[1] checkmate_2.3.3

loaded via a namespace (and not attached):
[1] compiler_4.5.1  backports_1.5.0 bspm_0.5.7