To avoid SCRIPT1010: Expected identifier in IE < 9

While trying Bootstrap-Tree out in IE10 developer mode emulating IE8 (lowest IE version supported by our project) I noticed that IE was throwing an error: SCRIPT1010: Expected identifier. It happened due to the dot notation for the attributes variable. Changed it to bracket notation and it worked like a charm.

This is my first edit on project that isn't my own, so I apologize if I am doing something incorrect. =)