build failed with kotlin.KotlinNullPointerException

[selmanon]

I get this issue after an update followed by a rollback against the Gradle version.

Background:
Bamboo builds with Docker run tasks.
Agent environment.

------------------------------------------------------------
Gradle 5.4.1
------------------------------------------------------------

Build time: 2019-04-26 08:14:42 UTC
Revision: 261d171646b36a6a28d5a19a69676cd098a4c19d

Kotlin: 1.3.21
Groovy: 2.5.4
Ant: Apache Ant(TM) version 1.9.13 compiled on July 10 2018
JVM: 1.8.0_161 (Oracle Corporation 25.161-b12)
OS: Linux 3.10.0-693.17.1.el7.x86_64 amd64

From 

classpath 'com.android.tools.build:gradle:3.5.3'
distributionUrl=https\://services.gradle.org/distributions/gradle-5.4.1-all.zip

To

classpath 'com.android.tools.build:gradle:4.2.0'
distributionUrl=https\://services.gradle.org/distributions/gradle-6.7.1-all.zip

gradlew assemble 

Project :APP already has a grgit property. Remove org.ajoberstar.grgit from either :APP or :APP. publishNonDefault is deprecated and has no effect anymore. All variants are now published.

any idea about a path to follow to solve this issue?

[selmanon · Accepted solution]

Solved by removing compileOnly 'com.github.pengrad:jdk9-deps:1.0' dependency which I added after upgrading to Android Studio 4.2.