Instead of an if block, you can also use an unless block that negates the specified condition.
Template:
<div>
{{#unless author}}
<h1>Unknown Author</h1>
{{else}}
<h1>{{author.firstName}} {{author.lastName}}</h1>
{{/unless}}
</div>
Data:
{
author: {
}
}
Result:
<div>
<h1>Unknown Author</h1>
</div>
