Bug in b2Fixture Refilter method

What steps will reproduce the problem?
1. Setup two block in stack
2. Change top blocks fixture filter to disable collisions between blocks.

What is the expected output? What do you see instead?
After that top block must fall down, but it is not.

What version of the product are you using? On what operating system?
Mac Os in firefox

Please provide any additional information below.
I fixed it.
The problem was in 
box2d.b2Fixture.prototype.Refilter = function ()
{
    if (this.m_body)
    {
        return;
    }
        ...
}

wront in:
if (this.m_body)

must be
if (!this.m_body)

Original issue reported on code.google.com by rackovy...@gmail.com on 5 Mar 2015 at 12:53

warpc3 / box2d-html5

Bug in b2Fixture Refilter method #4