fix #1278 onclick broken if Icon has no tooltip

When Icon widget had no tooltip, but `onclick` defined, the method was never invoked.

The commit only removes the conditional statement around delegate definition (ugly diff due to whitespace change)

close #1279
close #1366
as a general rule, I would always avoid to use a timeout where we can use `this.waitFor()`, in order to avoid issues with slower browser and to have faster tests in faster ones, even if in this case I don't think it would result in a problem.