jQuery object always represent value true whether object is empty or not

Due to missing check for length of jQuery object when quering for #modalContent IE throws a javascript error when closing modal window and trying to access nonexisting element.

Other browsers are a bit more relaxed throwing the error.

Checking for length solves the problem which also exists in the 7.x-1.x branch where problem originally was spotted.

Problematic code:
if ( $('#modalContent')) $('#modalContent').get(0).focus();