Changes in 3.1.5 to the loading indicator in assets/core.js have broken it.

Now, for example, when data-overlay="false" you get the JS error:
TypeError: undefined is not an object (evaluating '$loadingIndicator.fadeOut')

Caused by this change: https://github.com/phpbb/phpbb/commit/d978564600032cf599ef8e0352cdeb60312b2a10

Error comes from
https://github.com/phpbb/phpbb/blob/3.1.x/phpBB/assets/javascript/core.js#L398