nullfree plugin is broken in CircleCI

[vzurauskas]

Maven command:

mvn integration-test nullfree:nullfree -Pcheckstyle

It works when building locally, but in CircleCI build it results in this error:

[ERROR] Failed to execute goal com.nikialeksey:nullfree-maven-plugin:1.4.2:nullfree (default-cli) on project nereides-jackson: Can not get the origin from git repo.: Can not form the origin url. no protocol: [email protected]:vzurauskas/nereides-jackson.git -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal com.nikialeksey:nullfree-maven-plugin:1.4.2:nullfree (default-cli) on project nereides-jackson: Can not get the origin from git repo.
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:213)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:154)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:146)
    . . .
Caused by: java.net.MalformedURLException: no protocol: [email protected]:vzurauskas/nereides-jackson.git
    at java.net.URL.<init> (URL.java:593)
    at java.net.URL.<init> (URL.java:490)
    at java.net.URL.<init> (URL.java:439)
    at com.nikialeksey.goo.Goo.origin (Goo.java:47)
    at com.nikialeksey.nullfree.NullfreeMojo.execute (NullfreeMojo.java:37)

Currently it's disabled in .circleci/config.yml, .rultor.yml, pom.xml and readme.md. Fix it and re-enable.