Fix missing label of Files navigation sublist toggles

Signed-off-by: Jan C. Borchardt <hey@jancborchardt.net>

apps/files/templates/appnavigation.php

@@ -93,7 +93,10 @@ function NavigationListElements($item, $l, $pinned) {
 		NavigationElementMenu($item);
 	if (isset($item['sublist'])) {
 		?>
-			<button class="collapse app-navigation-noclose" <?php if (sizeof($item['sublist']) == 0) { ?> style="display: none" <?php } ?>></button>
+			<button class="collapse app-navigation-noclose"
+				aria-label="<?php p($l->t('Toggle %1$s sublist', $item['name'])) ?>"
+				<?php if (sizeof($item['sublist']) == 0) { ?> style="display: none" <?php } ?>>
+			</button>
 			<ul id="sublist-<?php p($item['id']); ?>">
 				<?php
 				foreach ($item['sublist'] as $item) {