Fix clicks on child elements of a tab

[chaitanyagupta]

I am using a bootstrap theme which has a slightly complex heirarchy of elements inside a tab:

<div class="card active show" data-toggle="tab" href="#content-1" role="tab">
  <div class="card-body">
    <h5>headline</h5>
    <p>Some more details</p>
  </div>
</div>

A click on any element inside the div.card-body doesn't work. This PR fixes that by using event.currentTarget instead of event.target.

Hope I have not broken any existing use case! If so, will be happy to fix it.

[thednp]

Will have a look at this after the week-end.

[Vuurvlieg]

@chaitanyagupta thanks for this PR, Looks like its the same 'bug' as in #242?

[chaitanyagupta]

@Vuurvlieg yes the issue does look very similar.

[thednp]

Hold on folks, just for a second. Yes this PR right here proves to be useful in this case, I just finished some testing with modern and some legacy browsers (I even found some unsolved and unrelated issues there), but this doesn't mean we change all handlers to work this way, as each handler has it's own quirks and whistles.

[thednp]

@chaitanyagupta do you have a demo to showcase my code is faulty? I want to see it before anything else.

[chaitanyagupta]

@thednp I have three versions of the same page for you. Click on any of the links under the "Features" heading on that page (i.e. Organize, Search, Unread Tasks, etc.)

1. First, take a look at http://deftask-design.deftask.com.s3-website.us-east-2.amazonaws.com/bootstrap/index.html#features
   This uses bootstrap.js. You will see that switching tabs works just fine.

2. Next look at http://deftask-design.deftask.com.s3-website.us-east-2.amazonaws.com/bn/index.html#features
   This uses bootstrap-native v4, but without my fixes. You will notice the issue as soon as you try switching tabs. If you look in the console, you will see an error similar to this: Uncaught TypeError: Cannot read property 'classList' of null

3. Lastly, look at http://deftask-design.deftask.com.s3-website.us-east-2.amazonaws.com/bn-tab-click-fix/index.html#features
   This uses bootstrap-native with my fixes. Now everything works perfectly.

Hope this demonstrates the issue effectively.

FWIW the bootstrap theme I am using is: https://themes.getbootstrap.com/product/wingman-landing-page-app-template/

[chaitanyagupta]

Just so you know, there is one more issue that I had to fix before I could get the demo working with this PR. It relates to not setting the aria-selected attribute correctly when switching tabs. However, its a tangential issue so I will file it separately.