Queue failing on resave of channel

Description

I have a Craft site that is getting an error when a resave on a channel is triggered:

Return value of craft\services\Assets::ensureFolderByFullPathAndVolume() must be of the type integer, null returned.

The issue seems to be related to the fact that it's using folders and subfolders in Assets, but I am not 100% sure. I have validated that the files exist in the filesystem.

Also, it seems irrelevant, but just in case, here is the content of the job:

{
    "elementType": "craft\\elements\\Entry",
    "criteria": {
        "siteId": 1,
        "sectionId": "2",
        "typeId": "2",
        "status": null,
        "enabledForSite": false
    },
    "description": "Resaving Blog - Blog entries"
}

Steps to reproduce

1. Create an asset in a subfolder.
2. Trigger resave on a channel with these assets.

Additional info

• Craft version: Craft Pro 3.0.38
• PHP version: 2.0.29
• Database driver & version: MySQL 5.6.41