Fix null pointer test in CloudStorageFileSystemProviderTest

[jart]

A null pointer is triggered from testNullness and therefore is disabled.

[mziccard]

@jart is this still an issue?

[jart]

Correct this is still an issue: https://github.com/GoogleCloudPlatform/gcloud-java/blob/master/gcloud-java-contrib/gcloud-java-nio/src/test/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystemProviderTest.java#L632

[lesv]

Updated Link https://github.com/GoogleCloudPlatform/google-cloud-java/blob/master/google-cloud-contrib/google-cloud-nio/src/test/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystemProviderTest.java

[lesv]

This relates to Storage, so I've marked it so. I don't think this blocks GA, but we should investigate and fix.