How do I check for an empty grid?

 <window id="empComment">
                    <groupbox id="gbComments" mold="3d">
                        <!--<style src="/widgets/layout/group_box/sprite.css.dsp" />-->
                        <!--<attribute name="onOpen"><![CDATA[arrow.setSclass("open-" + self.isOpen());]]></attribute>-->
                        <caption label="Comments">
                            <button id="commentAdd" label="+"/>
                        </caption>
                         <grid id="gridComments" sclass="myStyle">
                             <columns>
                                <column id="pwricmt_comment" label="Comment"/>
                                <column id="pwricmt_activity_date" label="Date/Time" />
                                <column id="pwricmt_user_id" label="User ID"/>

                             </columns>
                             <rows id="gridRows">
                                <row>

                                </row>
                             </rows>
                            </grid>
                    </groupbox>
                </window>

 empComments_gridComments.getChildren().clear()