Exception in thread "main" java.lang.NullPointerException + other question

[brodyFlannigan]

Hey there,
java-illiterate GTFS dude here.
I'm having an issue with the latest version of datatool-service-alerts.
Here's the error Java is throwing when I try to run datatools.jar

Exception in thread "main" java.lang.NullPointerException
at com.conveyal.gtfs.api.ApiMain.loadFeedsFromDirectory(ApiMain.java:133)
at com.conveyal.gtfs.api.ApiMain.initialize(ApiMain.java:101)
at com.conveyal.gtfs.api.ApiMain.initialize(ApiMain.java:69)
at com.conveyal.gtfs.datatools.ServiceAlerts.main(ServiceAlerts.java:57)

Also, what should I specify for the path to GTFS? The path to a folder containing each file (agency, trips, etc...) or the path to the latest version of my gtfs.zip?