Build errors when ossrhUsername is not set

Posted by deepakjois:

Reported by @peterstace on Slack:

$ ./gradlew build

FAILURE: Build failed with an exception.

* Where:
Build file '/home/petsta/r/dgraph4j/build.gradle' line: 148

* What went wrong:
A problem occurred evaluating root project 'dgraph4j'.
> Could not get unknown property 'ossrhUsername' for object of type org.gradle.api.publication.maven.internal.deployer.DefaultGroovyMavenDeployer.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

* Get more help at https://help.gradle.org

BUILD FAILED in 0s