[GREENFOOT-164] IllegalMonitorStateException when moving speedslider

Exception in thread "SimulationThread" java.lang.IllegalMonitorStateException at java.util.concurrent.locks.ReentrantReadWriteLock$Sync.tryRelease(ReentrantReadWriteLock.java:317) at java.util.concurrent.locks.AbstractQueuedSynchronizer.release(AbstractQueuedSynchronizer.java:1175) at java.util.concurrent.locks.ReentrantReadWriteLock$WriteLock.unlock(ReentrantReadWriteLock.java:992) at greenfoot.core.Simulation.runOneLoop(Simulation.java:212) at greenfoot.core.Simulation.run(Simulation.java:128)

---

Issue metadata

• Issue type: Bug
• Priority: Medium
• Fix versions: 1.4.6