Exception while migrating to Wildfly 14

Issue description as reported at https://github.com/emmartins/wildfly-server-migration/issues/10 :

"Hello I'm currently migrating from Wildfly 10.0.1 Final to Wildfly 14.0.0 Final and it seems your server migration tool does not recognize Wildfly 14. According to the latest changes this migration should be supported.

Steps I did:

download latest code base
mvn clean install
unzip jboss-server-migration-1.3.0-SNAPSHOT.zip
Next i started the migration via ./jboss-server-migration.sh -s /home/msommer/Schreibtisch/WildflyUpdatePoc/wildfly-10.1.0.Final -t /home/msommer/Schreibtisch/WildflyUpdatePoc/wildfly-14.0.0.Final/
Results:
Exception in console:
Retrieving servers... INFO SOURCE server name: WildFly Full, version: 10.1.0.Final. java.lang.IllegalArgumentException: WFCMTOOL000006: Failed to retrieve server TARGET, from base dir /home/msommer/Schreibtisch/WildflyUpdatePoc/wildfly-14.0.0.Final. at org.jboss.migration.core.ServerMigration.getServer(ServerMigration.java:186) at org.jboss.migration.core.ServerMigration.run(ServerMigration.java:134) at org.jboss.migration.cli.CommandLineServerMigration.main(CommandLineServerMigration.java:131)"