Gradle build's linkCheck task generates two (non-fatal) NullPointerExceptions in Gradle 6.6.1

When running a standard build of the jalview.jar (or beyond) using Gradle 6.6.1, the linkCheck task generates two NullPointerExceptions. These did not occur when using Gradle 6.5.0:

> Task :linkCheck
Could not read standard output of command '/home/bsoares/buildtools/jdk/jdk-14-linux-x64/jdk/bin/java'.
java.lang.NullPointerException
        at org.apache.tools.ant.util.TeeOutputStream.write(TeeOutputStream.java:86)
        at org.gradle.process.internal.streams.ExecOutputHandleRunner.forwardContent(ExecOutputHandleRunner.java:67)
        at org.gradle.process.internal.streams.ExecOutputHandleRunner.run(ExecOutputHandleRunner.java:53)
        at org.gradle.internal.operations.CurrentBuildOperationPreservingRunnable.run(CurrentBuildOperationPreservingRunnable.java:42)
        at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:64)
        at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:48)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
        at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:56)
        at java.base/java.lang.Thread.run(Thread.java:832)
Could not read error output of command '/home/bsoares/buildtools/jdk/jdk-14-linux-x64/jdk/bin/java'.
java.lang.NullPointerException
        at org.apache.tools.ant.util.TeeOutputStream.close(TeeOutputStream.java:51)
        at org.gradle.internal.concurrent.CompositeStoppable$2.stop(CompositeStoppable.java:90)
        at org.gradle.internal.concurrent.CompositeStoppable.stop(CompositeStoppable.java:106)
        at org.gradle.process.internal.streams.ExecOutputHandleRunner.forwardContent(ExecOutputHandleRunner.java:70)
        at org.gradle.process.internal.streams.ExecOutputHandleRunner.run(ExecOutputHandleRunner.java:53)
        at org.gradle.internal.operations.CurrentBuildOperationPreservingRunnable.run(CurrentBuildOperationPreservingRunnable.java:42)
        at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:64)
        at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:48)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
        at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:56)
        at java.base/java.lang.Thread.run(Thread.java:832)