ui: fix opening settings window in datastore panel

ui: fix opening settings window in datastore panel

When a user directly opened the webui with a fragment that is not
the summary, opening of the 'my settings' window fails because the
initial set of the columns field triggers a state change, which in turn
tries to trigger 'updateColumns'. That fails though, since the columns
were not even rendered yet (because we are on a different tab).

To fix this, simply return when the panel is not rendered yet.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>