Getting wrong validation message using Angular.js

Question

I have an issue.i am getting wrong validation message while using Angular.js. I am explaining my code below.

 <div class="input-group bmargindiv1 col-md-12">
<span class="input-group-addon ndrftextwidth text-right" style="width:180px">Member Type :</span>
 <select class="form-control"  id="nosofvoucher" ng-model="vouchers" ng-options="v.name for v in listOfMember track by v.value "  ng-change="generateCodeRange('nosofvoucher')" ng-disabled="dismember">
</select>
 </div>

my controller side code is given below.

$scope.listOfMember=[{
        name:'Select member type',
        value:''
    }]
    $scope.vouchers=$scope.listOfMember[0];
    $http({
        method:'GET',
        url:"php/selectMemberType.php",
        headers: { 'Content-Type': 'application/x-www-form-urlencoded' }
    }).then(function successCallback(response){
        //console.log('respo',response.data);
        angular.forEach(response.data,function(obj){
            var data={'name':obj.member_name,'value':obj.member_type};
            $scope.listOfMember.push(data);
        })
        $timeout(function(){
            var value={'name':'New Registered User','value':0};
            $scope.listOfMember.push(value);
        },2000)
    },function errorCallback(response) {
    })

but when i am checking the validation message even i am selecting the New Registered User from drop down still the validation message is saying Please add member type and the code is given below.

$scope.addGenerateCodeData=function(billdata){
     if($scope.vouchers.value==null || $scope.vouchers.value==''){
            alert('Please add member type');
            codeFieldFocus.borderColor('nosofvoucher');
    }
}

Here even after selecting the New Registered User from list the above validation message is executing which should not.Please help me to resolve this issue.