serialize not converting NA's to nulls for number type items

[collinschwantes]

Having an issue with data serialization where numeric NA values are not converted to nulls when serializing the data.
They are instead added as "NA".

### repex for jsonvalidate


json_schema <- '{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "Vector Competence Data Standard v1.0.0",
  "description":"A minimal flexible data standard viral vector competence studies",
  "type": "object",
  "properties": {
    "mean_temp_reared":{
        "description":"Average temperature recorded during rearing in celsius. See http://www.ebi.ac.uk/efo/EFO_0001702",
        "examples": [25.2, 30, 18, 27.6],
        "type":"array",
        "items":{
            "type": ["number", "null"],
            "minItems":1
          }
    }
  }
}'
 
num_data <- list("mean_temp_reared" = c(1,2,2.4,NA))

num_obj <- jsonvalidate::json_schema$new(schema = json_schema)

num_json <- num_obj$serialise(num_data)

num_obj$validate(num_json,verbose = TRUE)

Session info

R version 4.5.0 (2025-04-11)
Platform: aarch64-apple-darwin20
Running under: macOS Sequoia 15.7.4

Matrix products: default
BLAS:   /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib 
LAPACK: /Library/Frameworks/R.framework/Versions/4.5-arm64/Resources/lib/libRlapack.dylib;  LAPACK version 3.12.1

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

time zone: America/New_York
tzcode source: internal

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

loaded via a namespace (and not attached):
 [1] BiocManager_1.30.25 compiler_4.5.0      R6_2.6.1            tools_4.5.0        
 [5] rstudioapi_0.17.1   curl_6.2.3          Rcpp_1.0.14         V8_8.2.0           
 [9] jsonvalidate_1.5.0  jsonlite_2.0.0      renv_1.0.11