When "percent" field is NULL, show non breaking space instead of 0

[willemverspyck]

Subject

When using this code:

    protected function configureListFields(ListMapper $listMapper): void
    {
        $listMapper
            ->add('rate', TemplateRegistry::TYPE_PERCENT);
    }

And the value of "rate" is NULL, the current return value is "0 %". I think the value must be " " for NULL and "0 %" for 0. Also return " " when currency is NULL.

Same change for configureShowFields.

I am targeting this branch, because it's BC.

Changelog

### Changed
Twig templates: "list_percent", "show_percent", "list_currency" and "show_currency"

[VincentLanglet]

Why a nbsp ?

Suggested change

	{%- if value is null -%}
	 
	{%- else -%}
	{% set value = value * 100 %}
	{{ value }} %
	{%- endif -%}
	{%- if value is not null -%}
	{{ value * 100 }} %
	{%- endif -%}

Should be enough ?

[willemverspyck]

Years ago &nbsp was necessary to prevent problems with cells, but I don't think they are needed anymore. I used the same code as "display_datetime", "display_date" and "display_time" where also &nbsp is displayed when value is empty. Do you want me to change those too?

[VincentLanglet]

If we don't need them, let's avoid them indeed.
Elsewhere, but if it's for consistency, I won't block this PR.

[VincentLanglet]

Suggested change

	{%- if value is null -%}
	 
	{%- else -%}
	{{ field_description.options.currency }} {{ value }}
	{%- endif -%}
	{%- if value is not null -%}
	{{ field_description.options.currency }} {{ value }}
	{%- endif -%}

[VincentLanglet]

Thanks @willemverspyck