{% if not (content.field_name.isEmpty == true) and content.field_name.0 is defined %}
<div class="buy_cart">
{{ content.field_name.0['#url'] }}
</div>
{% else %}
<p> field is empty. </p>
{% endif %}
{% if not (content.field_name.isEmpty == true) and content.field_name.0 is defined %}
<div class="buy_cart">
{{ content.field_name.0['#url'] }}
</div>
{% else %}
<p> field is empty. </p>
{% endif %}