"An unknown server error has occurred" when creating a new space in Confluence 7.19.4

[Patricia Bascom]

I am a new server admin for JIRA/Confluence.  I looked at the articles on this issue from version 6 but I am seeing the issue in 7.19.4.  The users are able to create spaces using the direct link of https://<confluence base>/confluence/spaces/createspace-start.action?src=spacemenu.  My first issue is I'm not sure which logs I should look at to verify the issue and I am in a disconnected environment so I can't send logs.  I tried to disable and reenable the Confluence Space Blueprints Plugin.  I haven't tried the DB fixes as I'm not sure if this is where I should go next without looking at the logs.  

Any help at pointing me in the right direction of where to look would be appreciated.

[Patricia Bascom]

@Nicolas Grossi 

We ended up having to clean up the database for a solution, for some reason during one of the upgrades the DB no longer showed the confluence version.

The atlassian-confluence.log has a stack trace of java.lang.NullPointerException for URL: /confluence/rest/create-dialog/1.0/space-blueprint/dialog/web-items.
According to it, the Installation Date is null causing the issue.

added the date and we were good again.