fix lucky mode calling complete callback multiple times

As reported in #10, when in "lucky" mode, multiple "found" callbacks could still be called instead of the first one only

This fixes the issue from suite about Opera's array being 5 elements. When you make `planned = null` in L163 and the callback fires once again, `--this.planned` evaluates to `-1` and `oncomplete` is fired once again, and again over and over