There are several parts to this answer..

The first to note is that these are not errors they are warnings. In that respect they cause no processing issues and things run properly.

Next – I can only assume unless you tell me otherwise,  that you used the forum toolbox housekeeping to reset users new posts as we can find no other way to replicate the warnings. If this is the case then they should go away as your users log in and use the forum. And we do have a fix for the toolbox usage ready.

Most importantly however, is that no website should run with notices/warnings/errors being displayed to the screen. It is most unwise and, as a rule and principle, hosts should turn this off. So – unless you have the WP_DEBUG directive turned on in your wp-config.php file we strongly recommend that you talk to your host and have error display turned off as it should be.

nope i didnt use the toolbox and my debug was off but i just turned off site wide php errors and that worked.

We are just not sure how you would get that notice. It signifies a variable not set up properly. 

Bit harmless since not initialized is same as empty so it works perfectly except for the notice. 

Only methos we have seen so far for misinitialing the data was the housekeeping button – which is fixed for next version