Issue when running Processing

[tru489]

I followed the instructions on the Github page, and when running the .pde files in Processing, I got this error:

=================================================== G4P V4.0.4 created by Peter Lager

ControlP5 2.2.6 infos, comments, questions at http://www.sojamo.de/libraries/controlP5 ################ EXCEPTION IN EVENT HANDLER ################ An error occured during execution of the eventhandler: CLASS: openview_pulseox METHOD: start_click Caused by java.lang.NullPointerException openview_pulseox.start_click(openview_pulseox.java:829) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) java.lang.reflect.Method.invoke(Method.java:498) g4p_controls.GAbstractControl.fireEvent(Unknown Source) g4p_controls.GButton.mouseEvent(Unknown Source) g4p_controls.GWindowImpl.mouseEvent(Unknown Source) sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) java.lang.reflect.Method.invoke(Method.java:498) processing.core.PApplet$RegisteredMethods.handle(PApplet.java:1436) processing.core.PApplet.handleMethods(PApplet.java:1638) processing.core.PApplet.handleMouseEvent(PApplet.java:2749) processing.core.PApplet.dequeueEvents(PApplet.java:2652) processing.core.PApplet.handleDraw(PApplet.java:2493) processing.awt.PSurfaceAWT$12.callDraw(PSurfaceAWT.java:1547) processing.core.PSurfaceNone$AnimationThread.run(PSurfaceNone.java:313) ##############################################################

What would cause this error? I am using the version 2 pulse oximeter shield.