Upgrading maven-enforcer-plugin to 1.4.1 breaks maven-assembly-plugin

After upgrading m-e-p from 1.4 to 1.4.1 the maven-assembly-plugin generates the following error:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-assembly-plugin:2.4:single (assemble) on project extjars: Execution assemble of goal org.apache.maven.plugins:maven-assembly-plugin:2.4:single failed. NullPointerException -> [Help 1]

Downgrading to m-e-p 1.4 makes the assembly work again.

Sample pom & assembly that expose the error attached.

When called via:
mvn -Dplugins.maven-enforcer-plugin.version=1.4
a zip file is generated as expected, when called via
mvn -Dplugins.maven-enforcer-plugin.version=1.4.1
(or without argument) you will get the NPE.