Fix incorrect twig field checks for contacts and companies

[mollux]

Q	A
Bug fix? (use the a.b branch)	[x]
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 #13197

Description:

during the phptemplate to thig migration, some checks were not correcty converted, resulting in 500 errors when a field doesn't exist.
As Mautic allows to disable specific fields via the UI, this is a common usecase.

in PHP this works

if (!empty($fields['core']['city']['value'])):
    $location[] = $fields['core']['city']['value'];
endif;

but the equivalent in twig doesn't work, and throws a Twig\Error\RuntimeError

{% if fields.core.city.value is not empty %}
   {% set location = location|merge([fields.core.city.value]) %}
{% endif %}

This PR addresses this, by checking if the parent is defined.

questions for someone more familiar with twig

what is the proper way to check this?
is it

• {% if fields.core.city is defined %}
• {% if fields.core.city is defined and fields.core.city.value is defined %}
• {% if fields.core.city is defined and fields.core.city.value is defined and fields.core.city.value is not empty %}
• another option

This makes me wonder is we should provide a generic does exist is is not empty helper, to be able to check properly the whole structure?

Steps to test this PR:

1. Open this PR on Gitpod or pull down for testing locally (see docs on testing PRs here)
2. disable all fields except email, company name
3. create contacts, create companies, add contacts to companies, list company details, ...
4. verify no 500 Twig\Error\RuntimeError errorss are thrown

[escopecz]

Works as described. No error. I can create new contact and companies, edit them link them. We should probably disable unpublishing of company name as it's an identificator field that must be present. Next time...

Thank you! 👍