Fix a JS failure when the show pause preferences setting is disabled

[volha-pivavarchyk]

Q	A
Bug fix? (use the a.b branch)	[ ]
New feature/enhancement? (use the a.x branch)	[ ]
Deprecations?	[ ]
BC breaks? (use the c.x branch)	[ ]
Automated tests included?	[ ]
Related user documentation PR URL	mautic/mautic-documentation#...
Related developer documentation PR URL	mautic/developer-documentation#...
Issue(s) addressed	Fixes #...

Description:

If the Show pause contact preferences date is not enabled the JS will fail.

This commit fixes this and does some general JS improves that will help with readablility and maintainability.

Steps to reproduce:

1. Disable the "Show pause contact preferences" in Settings
2. Send a segment email
3. Click on the unsubscribe link
4. Try to switch on/off the "I want to receive email" option
5. A JS error will be shown in the console
   
   The fields will not be enabled/disabled
   

Steps to test this PR:

1. Open this PR on Gitpod or pull down for testing locally (see docs on testing PRs here)
2. The same steps as in the reproduction part
3. There is no the JS error. The fields can be enabled/disabled

[escopecz]

I have also fixed this bug in our fork recently. It's slightly different solution. I'd like to avoid conflicts. I cannot push it directly as it depends on other PR that hasn't been pushed yet. I'll try to push it to unblock.

[escopecz]

@volha-pivavarchyk this is our version of the same bug fix. Please take a look: #11443

[escopecz]

Let's go with this change as #11443 has too many dependent PRs and will take some time to merge.

The code looks great 👍

[jos0405]

Works. There is no JS error after PR.