sd2df() drops missing rows of data frames with a single character column

[ryanzomorrodi]

Describe the bug
When using sd2df() to transfer a single character column with missing values, all non-missing rows are dropped.

To Reproduce
Steps to reproduce the behavior:

1. Submit the following code

import saspy
import pandas as pd
print(saspy)
#> <module 'saspy' from '/home/user/.virtualenvs/r-saspy/lib/python3.12/site-packages/saspy/__init__.py'>
print(saspy.SAScfg)
#> /home/user/.virtualenvs/r-saspy/lib/python3.12/site-packages/saspy/sascfg_personal.py
print(saspy.list_configs())
#> ['/home/user/.virtualenvs/r-saspy/lib/python3.12/site-packages/saspy/sascfg_personal.py']
sas = saspy.SASsession()
#> Using SAS Config named: oda
#> SAS Connection established. Subprocess id is 52082
#> 
print(sas)
#> Access Method         = IOM
#> SAS Config name       = oda
#> SAS Config file       = /home/user/.virtualenvs/r-saspy/lib/python3.12/site-packages/saspy/sascfg_personal.py
#> WORK Path             = /saswork/SAS_work65D200002B81_odaws02-usw2-2.oda.sas.com/SAS_work830300002B81_odaws02-usw2-2.oda.sas.com/
#> SAS Version           = 9.04.01M7P08062020
#> SASPy Version         = 5.102.1
#> Teach me SAS          = False
#> Batch                 = False
#> Results               = Pandas
#> SAS Session Encoding  = utf-8
#> Python Encoding value = utf-8
#> SAS process Pid value = 11137
#> SASsession started    = Fri Mar 21 17:38:09 2025
#> 
#> 
example = pd.DataFrame({'A': ["hello", None, "hi"]})
sas.df2sd(example, "example", "work")
#> Libref  = work
#> Table   = example
#> Dsopts  = {}
#> Results = Pandas
sas.submitLST("PROC PRINT DATA = example; RUN;", results = "TEXT")
#> 
#>                                                            The SAS System                     Friday, March 21, 2025 10:38:00 PM   8
#> 
#>                                                             Obs    A
#> 
#>                                                              1     hello
#>                                                              2          
#>                                                              3     hi   
#> 
#> 
sas.sd2df("example", "work")
#> A
#> 0	hello
#> 1	hi

2. See that when using sd2df() missing rows are dropped instead of being retained as a None value.

[tomweber-sas]

Hey @ryanzomorrodi , I'm out for the next day or two, but I will look into this as soon as I get back.
Tom

[ryanzomorrodi]

All good, I was just writing tests for an R wrapper sasquatch and discovered this and thought I'd let you know.