Maven Plugin: sourceDocuments are not optional but required

[ascheman]

According to the docs the sourceDocuments should be optional, but leaving them out in the Maven project (see below), leads to a runtime error:

[INFO] --- htmlsanitycheck:2.0.0-rc4:sanity-check (sanity-check-generated-docs) @ jigsaw-examples-docs ---
[INFO] ======================================================================
[INFO] Parameters given to sanityCheck plugin from Maven buildfile...
[INFO] Files to check  : null
...
[INFO] Fail on errors  : true
[INFO] Excludes        : []
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  2.839 s
[INFO] Finished at: 2025-10-29T13:47:06+01:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.aim42.htmlSanityCheck:htmlSanityCheck-maven-plugin:2.0.0-rc4:sanity-check (sanity-check-generated-docs) on project jigsaw-examples-docs: org.aim42.htmlsanitycheck.MisconfigurationException: source documents must not be null -> [Help 1]

           <plugin>
                <groupId>org.aim42.htmlSanityCheck</groupId>
                <artifactId>htmlSanityCheck-maven-plugin</artifactId>
                <version>2.0.0-rc4</version>
                <executions>
                    <execution>
                        <id>sanity-check-generated-docs</id>
                        <phase>verify</phase>
                        <goals>
                            <goal>sanity-check</goal>
                        </goals>
                        <configuration>
                            <sourceDir>${project.build.directory}/generated-docs</sourceDir>
                            <failOnErrors>true</failOnErrors>
                        </configuration>
                    </execution>
                </executions>
            </plugin>