Incompatibility with nullway version upgrade

[emmileaf]

Opening issue to track compile error in PRs upgrading com.uber.nullaway:nullaway from 0.10.7
Blocked PRs: #3952 (previous: #3918)

> Task :jib-core:compileJava
/home/runner/work/jib/jib/jib-core/src/main/java/com/google/cloud/tools/jib/api/RegistryUnauthorizedException.java:47: error: [NullAway] returning @Nullable expression from method with @NonNull return type
    return (HttpResponseException) getCause().getCause();
    ^
    (see http://t.uber.com/nullaway )
/home/runner/work/jib/jib/jib-core/src/main/java/com/google/cloud/tools/jib/api/RegistryUnauthorizedException.java:47: error: [NullAway] dereferenced expression getCause() is @Nullable
    return (HttpResponseException) getCause().getCause();
                                             ^
    (see http://t.uber.com/nullaway )
2 errors