Your *boatReview* attribute is null. You need to assign a default value to it as I guess you want to take fresh input and not displaying data from server in edit mode.

<pre><code>&lt;aura:attribute 
        name="boatReview" 
        type="BoatReview__c" 
        access="private" 
        default="{'sobjectType':'BoatReview__c', 'Name':'', 'Comment__c':''}"/>
</code></pre>

For a quick check, you can comment the <code>&lt;form></code> and your page should load without error but form content will not render.