answer returning false while making field mandatory on resolve

[ABC6]

I am making field assigned to Non-mandatory while resolving when there is an external reference record attached over the related list of incident, for this i have written script include and client script and not getting solution

isUserMember: function() {

        var userGrp = new GlideRecord('sys_user_grmember');

        userGrp.addQuery('user', this.getParameter('sysparm_usr'));

        userGrp.addQuery('group', this.getParameter('sysparm_grp'));

        userGrp.setLimit(1);

        userGrp.query();

        if (userGrp.next()) {

            var incidentId = this.getParameter('sysparm_is_external_reference');

        var gr = new GlideRecord('u_external_references');

        gr.addQuery('u_task', incidentId);

        gr.setLimit(1);

        gr.query();

        // Check if there's an external reference for the incident

        if (gr.next()) {

            return true;

        } else {

            return false;

        }

    }

    else {

        return false;

    }

    },

Client Script

if (g_form.getViewName() == 'sow_incident_resolve_modal' || g_form.getViewName() == 'ui16_incident_resolve_modal') {

        if (isLoading || newValue === '') {

            g_form.setMandatory('comments', true);

            g_form.setMandatory('assignment_group', true);

        }

        if (g_form.getValue('assigned_to') == '') {

            var getGroup = new GlideAjax('ResetAssignee');

            getGroup.addParam('sysparm_name', 'isUserMember');

            getGroup.addParam('sysparm_usr', g_user.userID);

            getGroup.addParam('sysparm_grp', g_form.getValue('assignment_group'));

            getGroup.addParam('sysparm_is_external_reference',g_form.getUniqueValue());

            getGroup.getXML(FCRAssignmentGroup);

        }

    }

}

function FCRAssignmentGroup(response) {

    var ans = response.responseXML.documentElement.getAttribute("answer");

    alert(ans);

    if (ans == true || ans == 'true') {

        g_form.setMandatory('assigned_to', false);

    } else {

        g_form.setMandatory('assigned_to', true);

    }

}

[GopikaP]

I am referring to the current logged in user. Is that user part of the assignment group you selected?