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.