strange invisible entry on outlook 2016 -is it associated with avast pro?

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as you can see there is a blank entry right under the gmail entry.. here is a screenshot >
https://s23.postimg.org/4e40r4swr/screencapture.png
someone said that it appears when their antivirus is working
as you can see here>
https://www.wilderssecurity.com/threads/strange-folder-0w-25-in-outlook-2003.221282/

The user has avast premium.

Does anyone knows what this is and how to remove it?

thanks