rad parser displays empty sections with wrong version when a version is excluded from one tab group

## Summary
the rad parser will display an empty section with the wrong version selection under certain conditions. this confuses the user about which version applies to the text that follows the empty section.

## Process
1. create at least two sets of tabs in a document.
2. in the first set, include, e.g., "v3.2 Snap,v3.1 Snap"
3. in the second set, include only one, e.g., "v3.2 Snap"
4. Note that selecting "v3.2 Snap" on the first tab does not switch the "v3.2 Snap" tab, but does blank out the text inside that tab

## Current and expected result
as expected, not including a tab for those versions that don't apply to a tab group leaves the section blank (happening).
doing so, however, does not remove or change the tab from the previous selection, so the text following the tab group (which was not part of the tab group) appears to apply to the hidden version.

Reproduce the issue with two tab groups, excluding a version from the second group, and observe the selected tab and following text. Start by tracing the RAD parser's handling of version selection across tab groups; done means an excluded version cannot leave a misleading selection or make following text appear associated with it.

Written by the indexing model from the issue text.