Simplify missing value and update CI use pre instead of nightly. (#24)

* simplify missing value and update CI use pre instead of nightly.

* Set architecture to default to remove CI warning.

Author: lupemba

.github/workflows/CI.yml

@@ -25,13 +25,13 @@ jobs:
         version:
           - 'lts'
           - '1'
-          - 'nightly'
+          - 'pre'
         os:
           - ubuntu-latest
           - macOS-latest
           - windows-latest
         arch:
-          - x64
+          - default
     steps:
       - uses: actions/checkout@v4
       - uses: julia-actions/setup-julia@v2

src/InterfaceDataModel/variable.jl

@@ -46,7 +46,7 @@ function default_cf_attributes(
             missing_value = _auto_convert(T, missing_value)
         end
 
-        cf_attributes[:missing_value] = [missing_value]
+        cf_attributes[:missing_value] = missing_value
 
         if !fixed_size(R, field)
             cf_attributes[:_FillValue] = missing_value