I was able to figure out a solution, it may not be the best solution, but it is working for my app.
Using grails-app/views/_fields/date/_input.gsp
<%@ page defaultCodec="html" %>
<g:if test="${constraints.nullable == true}">
<g:datePicker name="${property}" value="${value}" precision="${constraints.attributes.precision}" years="${constraints.attributes.years}" default="none" noSelection="['': '']" />
</g:if>
<g:else>
<g:datePicker name="${property}" value="${value}" precision="${constraints.attributes.precision}" years="${constraints.attributes.years}"/>
</g:else>