Snap installs section is empty when metrics aren't available

[anasereijo]

Steps to reproduce the problem

• log in on snapcraft.io
• go to My published snaps page

Expected behaviour

• have a message telling the user that no metrics are available yet or hide that section until metrics are available

How it looks like

Specs

• URL: https://snapcraft.io/snaps
• Operating system: macOS Big Sur
• Browser: Chrome Version 92.0.4515.159

[jkfran]

We should have an empty state when there are no metrics