error when selecting an older version of a plugin - method 'getLastChangeDate' on null object

[atimmbeu]

What product versions and settings are you using when this issue occurs?
PluginManager with BBj 20.30

Server BBj Version: REV 20.30
Server Build: 11/04/2020 15:56
Client BBj Version: REV 20.30
Client Build: 11/04/2020 15:56

Steps to Reproduce
run the plugin manager
go to available plugins
select an older version of a plugin
What I Expected
an older version gets selected and can be installed

What Happened Instead