That is most likely caused by a bad shell extension, returning empty icons for everything when Opus asks Windows which icons to display.
Cloud storage tools seem to be the most common cause of this bug.
ShellExView is a tool you can use to list shell extensions and try disabling them. Look for ones that where the type involves icons, try disabling them, and then fully exit Opus (via File / Exit Directory Opus) and re-launch it to see if the problem is still there.
In some cases, clearing the icon cache may also help, if the issue is the Windows icon caching is corrupt and returning blanks.