I keep getting this annoying crash

[Qwertygiy]

java.lang.ArrayIndexOutOfBoundsException: 0
org.jbox2d.dynamics.Island.a(Island.java:86)
org.jbox2d.dynamics.PhysicsWorld.a(PhysicsWorld.java:573)
net.buildism.t.r(World.java:723)
net.buildism.af.h(Game.java:217)
net.buildism.f.p(Main.java:708)
net.buildism.MainApplet.run(MainApplet.java:220)
java.lang.Thread.run(Unknown Source)


Usually right after I set the ball rolling in my contraption.