sourceElement can become NULL in function clickHandler

[mgc8]

In the function clickHandler(clickEvent) at line 661 in piwik.js, the while loop executes

sourceElement = sourceElement.parentNode;

without checking sourceElement.parentNode. This can lead to sourceElement becoming NULL and errors in the following code.

A patch is simple enough:

--while ((tag = sourceElement.tagName) != 'A' && tag != 'AREA') {
++while ((sourceElement.parentNode) && ((tag = sourceElement.tagName) != 'A' && tag != 'AREA')) {

Thanks, Mihnea

[vipsoft]

True, but we attach the click handler using the anchor tags returned by document.links. So, the only time we could enter the loop is when the web site did something silly, i.e.,

tracker->addListener(clickable_non_anchor_element_with_no_anchor_element_ancestors).

[vipsoft]

(In [1243]) Fixes #814 - guard against:

addListener(clickable_non_anchor_element_with_no_anchor_element_ancestors)