Downloaded a plugin that doesn't work/ NullPointerException

I downloaded this plug and added to the plugins folder
http://imagejdocu.tudor.lu/plugin/segmentation/thresholding_by_connection/start

when i go to run the plugin this error is thrown in the console.

Exception in thread “Hysteresis_” java.lang.NullPointerException
at connectionthresholding_.adjustMaxThreshold(connectionthresholding_.java:647)
at connectionthresholding_.doUpdate(connectionthresholding_.java:1077)
at connectionthresholding_.run(connectionthresholding_.java:992)
at java.lang.Thread.run(Thread.java:748)
Any ideas?

Thank you