dirSubdirs breaks when functions added to the array prototype

I have code:

Array.prototype.unique = function (comparer) {
   //Function body, not important
}

The problem is that code in imce.js around line 100 picks the array prototype function as part of the array because the enumeration is done on the array as an object. This is what the code reads:

for (var i in subdirs) {//add subdirectories
      imce.dirAdd(prefix + subdirs[i], branch, true);
}

If the for ... in loop is used then a subdirs.hasOwnProperty(i) check should be made.