Test if partial / component / content file exists before using it.

{% if content("myContent") %}
  {% content "myContent" %}
{% else %}
  <other content here>
{% endif %}

{% if partial("myPartial") %}
  {% partial "myPartial" %}
{% else %}
  <other content here>
{% endif %}

{% if component("myComponent") %}
  {% component "myComponent" %}
{% else %}
  <other content here>
{{% endif %}