[MDEP-700] Fix possible NPE

**[Piotr Zygielo](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=pzygielo)** opened **[MDEP-700](https://issues.apache.org/jira/browse/MDEP-700?redirect=false)** and commented


---

**Affects:** 3.1.2

**Remote Links:**
- [GitHub PR #47
](https://github.com/apache/maven-dependency-plugin/pull/47)
