[patch][ccla] event.js: onmouseenter/leave broken on Firefox 2

[doughays]

Firefox 2 has a onmouseover/out bug where it spawns spurious events that have invalid relatedTarget values attached to the event object.
These bad events must be ignored in order for onmouseenter/leave to work correctly.

[doughays]

recreate testcase - patch the path to dojo.js before running

[doughays]

Run the test using Firefox 2 (I'm on winxp).
Move the mouse into the input box.
An enter console message is displayed (good), followed by a leave console message (very bad). When yoy mouse off the box, you get an enter message (bad), and a leave message (good).
This is only broken on Firefox 2. Other browsers including Firefox 3 are OK. The fix is simple: check for a valid node in the mouseover/out handlers before calling isDescendant.

[doughays]

patch to event.js

[bill]

This looks good to me; I think it can be checked in. Not sure if Scott will have time to review (IIRC he said that he was unfortunately too busy to work on stuff for the 1.2 release, although I think he did make some changes recently)

[doughays]

(In [14472]) Fixes #7216 !strict. Check for a valid node before calling dojo.isDescendant to avoid FF2 bug.

[blowery]

Just curious, but why a try catch instead of an if test? try catch is relatively expensive in js... probably doesn't hurt, but it caught my eye.

also, you removed my thanks. :P

[doughays]

If you check with an "if" then an exception will be thrown.