mounted is called twice, leading to registering listeners twice

[SystemKeeper]

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Steps to reproduce

1. Have notify_push enabled
2. Check the requests when you receive a new notification

Expected behaviour

Notification should only be queried once

Actual behaviour

Notifications are queried twice from the API. After investigating, mounted is called twice, leading to registering the listener for notify push twice.

E.g. duplicate registering on page load:

Duplicate data:

I am unable to reproduce the behavior in my dev instance (neither master, nor stable30), but I see it on 2 production instance, one that was recently updated to NC 31 RC 1, the other running NC 30.0.5.