So what is this you ask? Well, I did a little digging, I watched the Timer Job and the query it sent ( to the content database of the central admin site):
SELECT tp_WebPartTypeId, COUNT(1), tp_Assembly, tp_Class
FROM AllWebParts (NOLOCK)
WHERE tp_WebPartTypeId IS NOT NULL GROUP BY tp_WebPartTypeId, tp_Assembly, tp_Class
You get back a result set that has a null for the tp_Assembly column for the web part. What is this web part you ask, well it is the Microsoft.Office.Server.Search.WebControls.SearchTopologyView web part
in the Microsoft.Office.Server.Search, Version=18.104.22.168,
Culture=neutral, PublicKeyToken=71e9bce111e9429c assembly.
If you do a query to see where these 6 instance are:
where tp_WebPartTypeId = '8D6034C4-A416-E535-281A-6B714894E1AA'
You will see that the web part exists on two pages:
Open those pages, notice…It DOES exist!
Now, here is the funny thing – rerun the queries. As soon as you open those pages, the databsae gets updated and the error will go away. Weird!!!