Basically you are going over the top and doing too many on-demand scans, you can't stop avast doing its housekeeping.
The other thing if it has happened multiple times, it probably means you are running an on-demand scan every day, which on a resident on-access antivirus is a much depreciated requirement.
- With a resident on-access antivirus like avast, the need for frequent on-demand scans is much depreciated. For the most part the on-demand scan is going to be scanning files that would be otherwise be dormant or inert. If they were active files then the on-access file system shield would be scanning them before being created, modified, opened or executed.
I have avast set to do a scheduled weekly Quick scan (I have only ever seen this once), set at a time and day that I know the computer will be on (usually late in the day when avast is likely to have done its housekeeping). If for some reason my system wasn't on, no big deal I will catch up on the next scheduled scan.