AddController doesn't update the m_prev of head

[GoogleCodeExporter]

What steps will reproduce the problem?
1. world.AddController(contA)
2. world.AddController(contB)
3. world.RemoveController(contA)
4. contA.Step is still called at each world step beyond this point.

Add controller never updates contA.m_prev when contB is added. Subsequently, 
RemoveController(contA) call has no effect and contA remains on the list of 
controllers.

What is the expected output? What do you see instead?

I expect contA.Step to not be called from then on.

"Patch" (excuse the non-patch nature, added lines marked with '+'):

b2World.prototype.AddController = function (c) {
+  if( this.m_controllerList !== null ) {
+    this.m_controllerList.m_prev = c;
+  }
    c.m_next = this.m_controllerList;
    c.m_prev = null;
    this.m_controllerList = c;
    c.m_world = this;
    this.m_controllerCount++;
    return c;
}

Original issue reported on code.google.com by nzaluts...@amplify.com on 27 Mar 2015 at 4:26