DOCK-2442: Handle null version in Event

[svonworl]

Description
In dockstore/dockstore#5697, in the webservice, we added a Hibernate NotFound annotation to make dangling Event versions gracefully resolve to null. This PR modifies the UI to gracefully handle said nulls by substituting some generic text where the detailed description of the version would have gone.

We don't know what kind of reference the null represented, so the most future-proof generic text would be "a version". However, all of the Events with existing versions point to tags, so for now, it's probably relatively safe, and definitely less generic, to instead say "a tag". This PR implements the latter.

webservice_test=# select distinct v.referenceType from event join workflowversion as v on event.versionid = v.id;
 referencetype 
---------------
 TAG
(1 row)

webservice_test=# select distinct v.referenceType from event join tag as v on event.versionid = v.id;
 referencetype 
---------------
 TAG
(1 row)

Review Instructions
Find a user with a recent ADD_VERSION_TO_ENTRY event and view their profile. In the database event table, set the versionid of the corresponding row to 0. Reload the profile, and confirm that the event now contains the generic text description of the version.

Issue
https://ucsc-cgl.atlassian.net/browse/DOCK-2442
dockstore/dockstore#5623

Security
No concerns.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (31921a3) 40.41% compared to head (be20ad7) 40.49%.
Report is 1 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1854      +/-   ##
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+ Coverage    40.41%   40.49%   +0.08%     
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  Files          364      364              
  Lines        11261    11268       +7     
  Branches      2888     2891       +3     
===========================================
+ Hits          4551     4563      +12     
+ Misses        4411     4405       -6     
- Partials      2299     2300       +1     

see 6 files with indirect coverage changes

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[sonarcloud]

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0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication