NPE updating a rule from KieBase

hi ,I also encountered this problem, plz help to take a look. it cause the NPE in 100% of runnings test. but i'm not sure whether it is reasonable logic.

the pom.xml:

//drools version: 7.52 or 7.53
<dependency>
    <groupId>org.drools</groupId>
    <artifactId>drools-core</artifactId>
</dependency>
<dependency>
    <groupId>org.drools</groupId>
    <artifactId>drools-mvel</artifactId>
</dependency>

notice:
Plz note that modifing the import statement path in the variable `drlStr`

thanks