ARC file name appearing in url list

[ianmilligan1]

Describe the bug
When extracting a list of URLs in an ARC file, the filename appears among the list of URLs.

To Reproduce
Using the sample ARC found in our ant-resources repository, the following script:

import io.archivesunleashed._
import io.archivesunleashed.udfs._
RecordLoader.loadArchives("/Users/ianmilligan1/dropbox/git/aut-resources/Sample-Data/*.gz", sc).all()
  .select($"crawl_date", $"url")
  .show(10, false)

Leads to these responses:

+----------+-----------------------------------------------------------------------------------------------+
|crawl_date|url                                                                                            |
+----------+-----------------------------------------------------------------------------------------------+
|20060622  |filedesc://ARCHIVEIT-227-UOFTORONTO-CANPOLPINT-20060622205612-00009-crawling025.archive.org.arc|
|20060622  |http://www.gca.ca/indexcms/?organizations&orgid=27                                             |
|20060622  |http://www.ppforum.com/en/speeches/index.asp?theme=all&year=2003                               |
|20060622  |http://www.nosharia.com/telgraaf,%20nedeland_files/image010.gif                                |
|20060622  |http://www.canadianlandmine.org/french/french/n1kd.cfm                                         |
|20060622  |http://canadianactionparty.ca/temp/Important_Memos/Some_facts_about_the_Census.doc             |
|20060622  |http://coat.ncf.ca/our_magazine/links/53/smith_a.jpg                                           |
|20060622  |http://communist-party.ca/calendar/cal_week.php?op=week&date=2006-08-18&catview=0              |
|20060622  |http://www.nawl.ca/ns/en/documents/Pub_Brief_Antiterror01_en.doc                               |
|20060622  |http://www.conservative.ca/EN/1018/                                                            |
+----------+-----------------------------------------------------------------------------------------------+

The same behaviour is not found in WARC files.

Expected behavior
The filedesc probably shouldn't be in the results list here.

Environment information

• AUT version: HEAD
• OS: MacOS 11.3.1
• Java version: Java 11
• Apache Spark version: 3.0.0
• Apache Spark w/aut: --jars
• Apache Spark command used to run AUT: ./bin/spark-shell --jars ~/dropbox/git/aut/target/aut-0.90.2-SNAPSHOT-fatjar.jar

Additional context
@ruebot