Add check to avoid js error

[luigifab]

Description

This PR add a check to avoid a javascript fatal error when I merge and minify all backend javascript files into one single file.

OpenMage 20.0.5 / PHP 7.4.11 - 8.0.0

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All automated tests passed successfully (all builds are green)

[colinmollenhour]

Does the init happen later or should it be added to an event observer like onload?

[luigifab]

Function _initWindowElements via initialize is already triggered on page load (at the end of the file).
Perhaps it is better to add the check here:

Event.observe(window, 'load',  function() {
    productConfigure = new ProductConfigure();
});

[Flyingmana]

in any case I would think it needs to wait for it to exist, and not just skipping it?
I think the current place is already ok to add the check, but maybe add a retry logic with setTimeout.

[luigifab]

For my and standard usage, a setTimeout is useless. Because if product_composite_configure does not exist on page load, it will never exist.

[github-actions]

Unit Test Results

1 files  ±0  1 suites  ±0   0s ⏱️ ±0s
0 tests ±0  0 ✔️ ±0  0 💤 ±0  0 ❌ ±0 
6 runs  +4  4 ✔️ +2  2 💤 +2  0 ❌ ±0 

Results for commit e9eff3b. ± Comparison against base commit 6270dc4.