Changing version of (downgrading) package always says it failed even when it succeeded

[Gert-dev]

• I have read the README.md document
• I am using the latest version of Warehouse
• I am using the Flatpak package of Warehouse
• I have not found any other opened issues on the same topic

Describe the issue in detail

When I change the version of (downgrade) a package to an older version from the list, Warehouse always says it failed because errors occurred through a notification banner, but it actually did end up succeeding.

The 'error' being shown in the dialog is included below.

If applicable, provide steps to reproduce the issue

1. Go to Packages.
2. Select a random package.
3. Expand the Version row.
4. Click 'Change Version'
5. Select a different version from the current one and install it.
6. Enter password.
7. Observe notification banner being shown that updating failed.

Run flatpak run io.github.flattool.Warehouse in a terminal and if applicable, show any output

fr: 0.00
r: 0.0 , c: 0 , t: 1
=======================================
fr: 0.03
r: 0.03 , c: 0 , t: 1
=======================================
fr: 1.00
r: 1.0 , c: 0 , t: 1
=======================================
Error occurred while changing version
Note that '/var/lib/flatpak/exports/share' is not in the search path
set by the XDG_DATA_HOME and XDG_DATA_DIRS
environment variables, so applications may not
be able to find it until you set them. The
directories currently searched are:

- /root/.local/share
- /usr/local/share/
- /usr/share/

I haven't seen this message yet using common CLI commands such as flatpak update, but would be happy to test others. I found this Flatpak issue about it which suggests it can happen when running commands as sudo instead of without it - in any case I verified XDG_DATA_DIRS on my host contains this folder - the shell in the Flatpak doesn't, but I presume Flatpak is being spawned on the host because it manages software on the host.