When scanning from the context menu, I really miss a notification saying something like “Scan completed successfully; no malicious files found.” That would definitely make the program more user-friendly. But I realize it’s pointless to ask for that.
First, I’m an Avast user and not an Avast Team member.
Personally - With a resident (on-access) scanner the need for on-demand scans is much depreciated. For the most part dormant/inert files are being scanned, the other active files are going to be scanned by the resident shields when they are activated.
If you happen to run a Smart Scan you are almost certain to get something upon completion - That scam also looks for weaknesses which Avast now doubt has a paid option for said weaknesses.
Having posted in the General sub-forum there are no clues as to what Avast program (and version number) you are actually using ?