If you don't specify a regexp pattern to list files to exclude, the backup fails.

The catalina.out log file reports

19-Jul-2011 14:08:32 org.jvnet.hudson.plugins.thinbackup.ThinBackupMgmtLink doBackupManual
INFO: Starting manual backup.
Exception in thread "ThinBackup Worker Thread thread" java.lang.NullPointerException
at java.util.regex.Pattern.<init>(Pattern.java:1149)
at java.util.regex.Pattern.compile(Pattern.java:840)
at org.jvnet.hudson.plugins.thinbackup.backup.HudsonBackup.<init>(HudsonBackup.java:78)
at org.jvnet.hudson.plugins.thinbackup.ThinBackupPeriodicWork.backupNow(ThinBackupPeriodicWork.java:95)
at org.jvnet.hudson.plugins.thinbackup.ThinBackupMgmtLink$1.execute(ThinBackupMgmtLink.java:74)
at org.jvnet.hudson.plugins.thinbackup.hudson.model.AsyncPeriodicWork$1.run(AsyncPeriodicWork.java:58)
at java.lang.Thread.run(Thread.java:636)

As a workaround, i've specified ^$ as the file pattern