Remove empty elements from comma-separated list

Updates the list parsing in Configuration to remove empty strings
from the comma-separated list. This will allow creating a single-
element list by appending a `,` after the element.

Refs: NOAA-EMC/global-workflow#2795

src/wxflow/configuration.py

@@ -172,7 +172,7 @@ def cast_as_dtype(string: str) -> Union[str, int, float, bool, Any]:
 
     if ',' in string:
         # Convert comma-separated list to python list
-        return [cast_as_dtype(elem.strip()) for elem in string.split(',')]
+        return [cast_as_dtype(elem.strip()) for elem in string.split(',') if elem.strip() != '']
 
     def _cast_or_not(to_type: Any, string: str):
         try:

tests/test_configuration.py

@@ -32,7 +32,7 @@
 export SOME_BOOL6=.F.
 export SOME_LIST1="3, 15, -999"
 export SOME_LIST2="0.2,3.5,-9999."
-export SOME_LIST3="20221225, 202212251845"
+export SOME_LIST3="20221225, 202212251845,"
 export SOME_LIST4="YES, .false., .T."
 export SOME_LIST5="0.2, test_str, 15, 20221225, NO"
 """