Add beans.xml to META-INF or WEB-INF to enable Contexts and Dependency Injection(CDI) for the Java EE Platform. This will avoid NullPointerException while injecting.

beans.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://java.sun.com/xml/ns/javaee"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="
      http://java.sun.com/xml/ns/javaee 
      http://java.sun.com/xml/ns/javaee/beans_1_0.xsd">
</beans>