sortArtifactByName: artifacts with the same name are lost

[lrozenblyum]

SCENARIO:
Try executing
mvn license:add-third-party -Dlicense.sortArtifactByName=true

on a project like this:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.leokom</groupId>
	<artifactId>license-plugin</artifactId>
	<version>10.0.0-SNAPSHOT</version>
	<packaging>jar</packaging>
	<properties>
		<smack.version>4.1.6</smack.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.igniterealtime.smack</groupId>
			<artifactId>smack-core</artifactId>
			<version>${smack.version}</version>
		</dependency>
		<dependency>
			<groupId>org.igniterealtime.smack</groupId>
			<artifactId>smack-extensions</artifactId>
			<version>${smack.version}</version>
		</dependency>
		<dependency>
			<groupId>org.igniterealtime.smack</groupId>
			<artifactId>smack-tcp</artifactId>
			<version>${smack.version}</version>
		</dependency>
		<dependency>
			<groupId>org.igniterealtime.smack</groupId>
			<artifactId>smack-java7</artifactId>
			<version>${smack.version}</version>
		</dependency>
	</dependencies>
</project>

EXPECTED:
the result license file contains multiple lines for Smack and XMPP dependencies

ACTUALLY:
the result license file contains just single lines for Smack and XMPP.
For example org.igniterealtime.smack:smack-extensions:4.1.6 is missed

Workaround: disabling license.sortArtifactByName solves the problem (but we lose the sorting then)