Fix show_trial_reminder?

[gonzaloriestra]

This PR caused the dashboard to show an error:

The error raises here:

cartodb/lib/assets/javascripts/new-dashboard/core/trackers.js

Line 26 in 1465b27

userInTrialPeriod: store.state.user.show_trial_reminder.toString()

And the problem is that show_trial_reminder? was returning null sometimes. The fix consists in making the method to always return true or false.

To ensure it works, we have to enable track.js for Staging (in app_config.yml).

[gonzaloriestra]

✔️ Acceptance OK

• Reproduced the issue in staging by enabling Track.js
• Applied the fix and checked that it works