title: FormRequest method to ignore null field upon validation in L5.4
body: <p>I've a Form Request with this rule:</p>
  
  <pre><code>"password" =&gt; "confirmed"
  </code></pre>
  
  <p>This solution works well in L5.3 because the rule itself has a bug, if you pass two empty fields like</p>
  
  <pre><code>"password" =&gt; "",
  "password_confirmation" =&gt; ""
  </code></pre>
  
  <p>they will be validated because both are empty strings (<code>""</code>).
  Even though this is a bug, I guess, it's fine in a certain degree because my application does other checks after the request anyway but in L5.4 every empty fields are converted to <code>null</code> and the <code>"confirmed"</code> rule alone does not work anymore because of the new middleware.</p>
  
  <p>I tried:</p>
  
  <pre><code>"password" =&gt; "sometimes|confirmed"
  </code></pre>
  
  <p>but it does not work because the key exists.</p>
  
  <p>My question is simple:</p>
  
  <blockquote>
    <p>Is there a validation rule that works similar to <code>sometimes</code> but it checks nullable values instead?</p>
  </blockquote>
  
  <p>I would like to keep the middleware though.</p>