[FIX] web_editor: fix editor-lock after gallery image reordering again

The bug was already solved with [1] but was reintroduced later for
another reason. [1] solved the problem by checking that the current
option is not destroyed before asking for an UI update thanks to a
trigger_up (the option was destroyed because of image reordering). The
bug is now reintroduced for the same basic reason: a new trigger_up was
added between the potential option destroy and the destroy check, so
if the option is destroyed, that trigger_up fails to be triggered and
the editor is locked.

This commit solves the problem once and for all, hopefully, with a
more robust solution: only destroy options when none is being
processed. That way we ensure that all trigger_up occuring during an
option activation / update can be properly done.

[1]: https://github.com/odoo/odoo/commit/9eeea4c4107dc15984c475582d5ee58a17cd2568

X-original-commit: 7770430f78ee9e122a732fa042226d362467158e