generateChangeLog without changeLogFile - better error message

When trying to generate a change log without a specified changeLogFile, I get a following error message:
Unexpected error running Liquibase: Unknown Reason

I believe that it would be better to inform a user that she is missing a changeLogFile.

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Without a logLevel debug, I get only the message above.

c:\Users\Honza\progz\liquibase-3.2.0>liquibase.bat --driver=org.sqlite.JDBC --url=jdbc:sqlite:c:\tmp\sqlite-ci.s3db --logLevel=debug generateChangeLog
DEBUG 11.7.14 0:35: liquibase: Connected to null@jdbc:sqlite:c:\tmp\sqlite-ci.s3db
DEBUG 11.7.14 0:35: liquibase: Setting auto commit to false from true
Unexpected error running Liquibase: Unknown Reason

SEVERE 11.7.14 0:35: liquibase: Unknown Reason
java.lang.NullPointerException
at java.io.File.<init>(Unknown Source)
at liquibase.integration.commandline.Main.doMigration(Main.java:894)
at liquibase.integration.commandline.Main.run(Main.java:170)
at liquibase.integration.commandline.Main.main(Main.java:89)

For more information, use the --logLevel flag

c:\Users\Honza\progz\liquibase-3.2.0>liquibase.bat --driver=org.sqlite.JDBC --url=jdbc:sqlite:c:\tmp\sqlite-ci.s3db --changeLogFile=c:\tmp\sqlite-ci-changelog.xml generateChangeLog
Liquibase 'generateChangeLog' Successful