get_terms and "child_of" issue on WP 4.2

Hello, I have a problem with the “get_terms” when I use “child_of” since I installed version 4.2 of wordpress. The error is as follows

Fatal error: Maximum execution time of 30 seconds exceeded in
mywebsite.com/wp-includes/taxonomy.php on line 3958.

The term used in ‘child of “a lot of children and up to 2 levels and is itself a child of another term.
The line in question is in /wp-includes/taxonomy.php this:

// Do not recurse if we've already APPROBATION the term as a child - this Indicates a loop.
if (in_array ($ term-> term_id, $ ancestors)) {
continue;
}

When I commented these lines I have no problem. Looking in the version 4.1.3, I feel that the function in question has been rewritten. It would there be a problem with “in_array”?
Do you have an idea to solve my problem? thank you!
Sorry for my english…