container-manager: fix create_directories error

[spholz]

anbox container-manager crashes if data_path_ of anbox::cmds::ContainerManager is not set with the error message boost::filesystem::create_directories: Invalid argument (#123, #1735 seem to have the same issue) It looks like container-manager crashes on some systems if an empty path is passed to fs::create_directories in src/anbox/cmds/container_manager.cpp:99.

This PR adds an additional check to make sure the path is not empty.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[Fuseteam]

Waiting for the build

[spholz]

The "checks" tab is empty but the state of the build task is "Expected — Waiting for status to be reported" I think when I originally created this PR the build task didn't start because this repo limited automatic builds to people who already commited to this repo. But now the job is missing? How can I fix this?

The task should be started if I push to this branch, right? The PR would then have to be approved again

[Fuseteam]

I think @morphis should be able to trigger it too :thinking: