WSO2 ESB how to sending array list empty error - wso2

Question

I Configurate url like:
https://htygnfgvsccl.com:6753/intellige/vehicle/getAlerts
this url some times getting data like
{
"alertsList": [
{
"vehicleNo": "45342",
"alertName": "Stop Skipped",
"depotName": "akividu"
},
{
"vehicleNo": "674894",
"alertName": "Stop Skipped",
"depotName": "guntur"
}
]
}
but some times getting data like
{
"alertsList": []
}
every time response code is 200 but how to send with error message in the case of alertsList empty
vehiclegetAlertsapi
<?xml version="1.0" encoding="UTF-8"?>
<api context="/intellige/vehicle/getAlerts" name="vehiclegetAlertsapi" xmlns="http://ws.apache.org/ns/synapse">
<resource methods="GET">
<inSequence>
<property description="http" name="HTTP_SC" scope="axis2" type="STRING" value="404"/>
<log level="full"/>
<send>
<endpoint key="vehiclegetAlertsendpoint"/>
</send>
</inSequence>
<outSequence>
<switch source="get-property('axis2','HTTP_SC')">
<case regex="200">
<log description="200log" level="custom">
<property expression="$ctx:ERROR_CODE" name="200reserrorcode"/>
</log>
<send/>
</case>
<default>
<log description="reslog" level="custom">
<property expression="$ctx:ERROR_CODE" name="reserrorcode"/>
<property expression="$ctx:ERROR_MESSAGE" name="reserrormessage"/>
<property expression="get-property('axis2','HTTP_SC')" name="reshttpsc"/>
</log>
</default>
</switch>
<clone continueParent="true">
<target>
<sequence>
<sequence key="vehiclegetAlertsmail"/>
</sequence>
</target>
</clone>
<send/>
</outSequence>
<faultSequence>
<switch source="get-property('axis2','HTTP_SC')">
<case regex="200">
<log description="200log" level="custom">
<property expression="$ctx:ERROR_CODE" name="200reserrorcode"/>
</log>
</case>
<default>
<log description="reslog" level="custom">
<property expression="$ctx:ERROR_CODE" name="reserrorcode"/>
<property expression="$ctx:ERROR_MESSAGE" name="reserrormessage"/>
<property expression="get-property('axis2','HTTP_SC')" name="reshttpsc"/>
</log>
</default>
</switch>
<clone continueParent="true">
<target>
<sequence>
<sequence key="vehiclegetAlertsmail"/>
</sequence>
</target>
</clone>
<send/>
</faultSequence>
</resource>
</api>
vehiclegetAlertsendpoint
<?xml version="1.0" encoding="UTF-8"?>
<endpoint name="vehiclegetAlertsendpoint" xmlns="http://ws.apache.org/ns/synapse">
<http method="get" uri-template="https://htygnfgvsccl.com:6753/intellige/vehicle/getAlerts "/>
</endpoint>
vehiclegetAlertsmail:
<?xml version="1.0" encoding="UTF-8"?>
<sequence name="vehiclegetAlertsmail" trace="disable" xmlns="http://ws.apache.org/ns/synapse">
<log level="custom">
<property name="status" value=" vehileget alert Details Sending mail"/>
</log>
<property expression="get-property('axis2','HTTP_SC')" name="ErrorMessage" scope="default" type="STRING" xmlns:ns="http://org.apache.synapse/xsd"/>
<property name="messageType" scope="axis2" type="STRING" value="application/json"/>
<property name="ContentType" scope="axis2" type="STRING" value="text/plain"/>
<property name="Subject" scope="transport" type="STRING" value="vehileget alert api not working"/>
<property name="OUT_ONLY" scope="default" type="STRING" value="true"/>
<property name="FORCE_SC_ACCEPTED" scope="axis2" type="STRING" value="true"/>
<payloadFactory media-type="json">
<format>{"vehileget alert api not working":"$1"}</format>
<args>
<arg evaluator="xml" expression="$ctx:ErrorMessage" xmlns:ns="http://org.apache.synapse/xsd"/>
</args>
</payloadFactory>
<call>
<endpoint key="vehiclegetAlertsmailid"/>
</call>
<drop/>
</sequence>
vehiclegetAlertsmailid:
<?xml version="1.0" encoding="UTF-8"?>
<endpoint name="vehiclegetAlertsmailid" xmlns="http://ws.apache.org/ns/synapse">
<recipientlist>
<endpoint>
<address uri="mailto:aisha#gmail.com"/>
</endpoint>
</recipientlist>
</endpoint>
get 200 response code send the data automatically in case if any other reponse to send the mail my mail id ,prsent my problem is my rest url some time total data like alertsList with data comming some times only alertsList comming not comming data that case how to send mail