Fix js error in modal popup

We have to close div's tags after line 

     $str[] = '<input type="hidden" name="' . $this->name . '" id="' . $this->id . '" value="' . $value . '" />';

otherwise we get a js error in "fabrikmodalrepeat.js" ( in J2.5).

HTML output before was 

```
<div class="button2-left">
	<div class="blank">
               <a id="jform_params_list_search_elements_modal_button" data-modal="jform_params_list_search_elements_modal">Select</a>
	</div>
</div>
<input type="hidden" name="jform[params][list_search_elements]" id="jform_params_list_search_elements" value="null" />
```
now is
```
<div class="button2-left">
	<div class="blank">
               <a id="jform_params_list_search_elements_modal_button" data-modal="jform_params_list_search_elements_modal">Select</a>
               <input type="hidden" name="jform[params][list_search_elements]" id="jform_params_list_search_elements" value="null" />
	</div>
</div>
```

I tested it in both J3 and J2.5, it doesn't break J3 and fix the error in J2.5.