title: Getting NullPointerException from Hashtable while using GObject method
body: <p>So I try to create a small Zombie-Shooter game. I use a GTurtle class from ACM package (jtf.acm.org). I have additional thread for a GTurtle, which is a GObject. I have a run method with while loop, that is checking if boolean is true, if it is - this.forward() method gets executed.</p>
  
  <p>I tried running game and pressing button, if it is W or D, boolean in GTurtle object gets changed and Thread executes action. Then I get this exception:</p>
  
  <pre><code>java.lang.NullPointerException
           at java.util.Hashtable.put(Hashtable.java:394)
           at acm.util.JTFTools.pause(JTFTools.java)
           at acm.util.Animator.delay(Animator.java)
           at acm.graphics.GTurtle.setLocation(GTurtle.java)
           at acm.graphics.GObject.move(GObject.java)
           at acm.graphics.GTurtle.move(GTurtle.java)
           at acm.graphics.GObject.movePolar(GObject.java)
           at acm.graphics.GTurtle.forward(GTurtle.java)
           at anotherTryJava.Player.run(Player.java:20)
           at java.lang.Thread.run(Thread.java:662)
  </code></pre>