Handling empty values
If a value of a custom field is empty, its corresponding metafield does not exist.
A test for that particular custom field will not return anything ("nil" in Liquid terms) and which gives you a nice clean syntax for checking if a given field has a value:
{% if product.metafields.accentuate.title %} <h1>{{ product.metafields.accentuate.title }}</h1> {% endif %}
This is a little different for repeatable fields. If you are testing to see if an element in a repeatable field has a value, you need to test if the element's value is either an empty string or null, both of which can be tested via the length of the element's value:
{% for ingredient in product.metafields.accentuate.ingredients %} {% if ingredient.size > 0 %} <p>{{ ingredient }}</p> {% endif %} {% endfor %}
And, if you are testing to see if a repeatable field has any elements at all:
{% if product.metafields.accentuate.ingredients.size == 0 %} <p>No ingredients have been added</p> {% endif %}
Please see https://shopify.github.io/liquid/filters/size/ for details on using the size filter.