Fixing the null pointer

components/device-mgt/org.wso2.carbon.device.mgt.extensions/src/main/java/org/wso2/carbon/device/mgt/extensions/device/type/template/dao/DeviceTypePluginDAOImpl.java

@@ -241,11 +241,13 @@ public class DeviceTypePluginDAOImpl implements PluginDAO{
     }
 
     private String getPropertString(List<Device.Property> properties, String propertyName) {
+        if (properties != null) {
             for (Device.Property property : properties) {
                 if (property.getName() != null && property.getName().equals(propertyName)) {
                     return property.getValue();
                 }
             }
+        }
         return null;
     }