Exporting table replaces empty string with NULL values

Exporting the mediawiki database (https://www.dolthub.com/repositories/timsehn/media_wiki/query/main?active=Tables&q=select+*+From+categorylinks+limit+100%3B) gave me a CSV that has NULL values instead of empty strings.

I assume this is a table export bug, but it could be a DoltHub bug also.

found:
```
cl_from,cl_to,cl_sortkey,cl_sortkey_prefix,cl_timestamp,cl_collation,cl_type
13305,Linguistic_morphology,MORPHOPHONOLOGY,,2024-03-12 02:10:51,uppercase,page
13305,Morphophonology, MORPHOPHONOLOGY, ,2024-03-12 02:10:51,uppercase,page
13305,Orthography,MORPHOPHONOLOGY,,2024-03-12 02:10:51,uppercase,page
13305,Phonology,MORPHOPHONOLOGY,,2024-03-12 02:10:51,uppercase,page
13306,Glass_applications,MIRROR,,2024-03-12 02:10:52,uppercase,page
```

expected:
```
cl_from,cl_to,cl_sortkey,cl_sortkey_prefix,cl_timestamp,cl_collation,cl_type
13305,Linguistic_morphology,MORPHOPHONOLOGY,'',2024-03-12 02:10:51,uppercase,page
13305,Morphophonology, MORPHOPHONOLOGY,'',2024-03-12 02:10:51,uppercase,page
13305,Orthography,MORPHOPHONOLOGY,'',2024-03-12 02:10:51,uppercase,page
13305,Phonology,MORPHOPHONOLOGY,'',2024-03-12 02:10:51,uppercase,page
13306,Glass_applications,MIRROR,'',2024-03-12 02:10:52,uppercase,page
```