Compiling the event listener sample project fails

aswan@aswan event-listener-example % mvn clean package
[MVNVM] Using maven: 3.6.3
[INFO] Scanning for projects...
[WARNING] 
[WARNING] Some problems were encountered while building the effective model for com.atlassian.crowd.example:crowd-event-listener-example:atlassian-plugin:1.0-SNAPSHOT
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-compiler-plugin is missing. @ line 42, column 21
[WARNING] 
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING] 
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[WARNING] 
[INFO] 
[INFO] ------< com.atlassian.crowd.example:crowd-event-listener-example >------
[INFO] Building event-listener-example 1.0-SNAPSHOT
[INFO] --------------------------[ atlassian-plugin ]--------------------------
[INFO] 
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ crowd-event-listener-example ---
[INFO] 
[INFO] --- maven-crowd-plugin:3.3.4:copy-bundled-dependencies (default-copy-bundled-dependencies) @ crowd-event-listener-example ---
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.253 s
[INFO] Finished at: 2020-09-07T16:41:28+10:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal com.atlassian.maven.plugins:maven-crowd-plugin:3.3.4:copy-bundled-dependencies (default-copy-bundled-dependencies) on project crowd-event-listener-example: Unable to execute mojo: UnsupportedOperationException -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException