ERR_EMPTY_RESPONSE when editing post

I have found the problem, except it should not be a problem. In the post-expirator plugin at about line 290 in the main php file there are two for loops of the form:

for (var i=0; i<max; i++) {
    cats[i].disabled = 'disable';
  }

If I change the code to

var i;
  for (i=0; i<max; i++) {
    cats[i].disabled = 'disable';
  }

It works fine. This should not make any difference. I suspect a problem with the chrome js interpretor.

P.S.
I find that what actually makes the difference is having a line, even a comment line between the line that sets the maximum value for the loop, and the loop itself, e.g. the following also fixes the problem

var max = cats.length;
// This is some dummy text which ensures the for loop works OK
   for (var i=0; i<max; i++) {
     cats[i].disabled = '';
	}