Partial download feature - error downloading IWP geopackage

[shirlysteph]

See screenshots below of errors when download IWP of different resolution in Geopackage format. These are screenshots provided by Macall Hock during testing. More details to follow once I have debugged and traced the issue.

[robyngit]

@shirlysteph I think the issue is that we don't have any z-level 12 geopackage files. They are only available for the max resolution, z-15. I outlined this issue in #2666:

Currently, we display all zoom levels 0–15 regardless of whether they're supported by a given format in a given layer. For example, we allow users to attempt to download z-level 0 to 14 geopackage tiles, even though they don't exist (we only have z-15 for most geopackage datasets). This results in a 404 error for all requests without much of an explanation.

Do you think this bug is a duplicate of that already documented issue + proposed solution?

[robyngit]

Closing this as a duplicate of #2666