Fixes #1562; remove some dead code
No longer fire change event when .select2('data', falsyValue) is called without the 3rd param;
Dead code removed: !"" is true.
data method use the same triggerChange logic as val method
Merge pull request #1563 from UltCombo/1562

Fixes #1562 do not trigger change on $().select2('data') unless specified with the second param