[3.0] Stop drawing an empty tab menu with an unresolved label

[albertlast]

Description

Admin and moderation pages whose menu has no title of its own drew a mobile tab menu containing nothing, labelled with the literal text {label} Menu. Straight off Admin → Scheduled Tasks:

<a class="mobile_generic_menu_1_tabs">
	<span class="menu_icon"></span>
	<span class="text_menu">{label} Menu</span>
</a>
…
		<ul class="dropmenu dropdown_menu_1_tabs">
		</ul>

Two lists with the same name

The block is guarded on Utils::$context['tabs'] but draws $tab_context['tabs']:

if (!empty(Utils::$context['tabs'])) {
	…
	foreach ($tab_context['tabs'] as $sa => $tab) {

They are not the same list. Utils::$context['tabs'] is set as a side effect of drawing the menu itself, from whichever area is selected:

// template_generic_menu_dropdown_above()
if (!empty($area['selected']) && empty(Utils::$context['tabs'])) {
	Utils::$context['tabs'] = $area['subsections'] ?? [];
}

$tab_context['tabs'] is only assembled from it inside the if (!empty($tab_context['title'])) branch further up. So on a page that has subsections but no tab title, the first is full and the second was never built — the guard passes, the loop finds nothing.

And why the label stayed raw

$tab_context['title'] was never set either, so the call passes ['label' => null]. Localization\MessageFormatter::formatMessage() filters its arguments before handing them over:

->format(array_filter($args, 'is_scalar'))

is_scalar(null) is false, so the argument is dropped, and ICU leaves an unmatched placeholder in the output rather than substituting an empty string. Reproduced directly — ['label' => null] through intl gives " Menu", but with the argument filtered out it gives "{label} Menu".

The guard now names the list that actually gets drawn, and the label falls back to '' so the same thing cannot happen if a menu ever gets tabs without a title.

Checked

Four pages on the running forum. {label} no longer appears anywhere, Scheduled Tasks draws no #adm_submenus at all, and the pages that do have tabs are untouched:

<span class="text_menu">Reported Members Menu</span>
<span class="text_menu">Manage Members Menu</span>
<span class="text_menu">Features and Options Menu</span>

Found by sweeping every rendered page of a stock forum for unsubstituted {placeholders}. This is one of the three the sweep turned up.

GenericMenu.template.php is also touched by #9392, which makes this element a nav landmark; the two do not overlap.

Issues References (Fixes|Related|Closes)

Related to #7933