Fix target attribute does not exists

Signed-off-by: Carl Schwan <carl@carlschwan.eu>

core/templates/layout.user.php

@@ -69,7 +69,7 @@ $getUserAvatar = static function (int $size) use ($_): string {
 					<?php foreach ($_['navigation'] as $entry): ?>
 						<li data-id="<?php p($entry['id']); ?>" class="hidden" tabindex="-1">
 							<a href="<?php print_unescaped($entry['href']); ?>"
-								<?php if ($entry['target']): ?> target="_blank" rel="noreferrer noopener"<?php endif; ?>
+								<?php if (isset($entry['target']) && $entry['target']): ?> target="_blank" rel="noreferrer noopener"<?php endif; ?>
 								<?php if ($entry['active']): ?> class="active"<?php endif; ?>
 								aria-label="<?php p($entry['name']); ?>">
 									<svg width="24" height="20" viewBox="0 0 24 20" alt=""<?php if ($entry['unread'] !== 0) { ?> class="has-unread"<?php } ?>>
@@ -106,7 +106,7 @@ $getUserAvatar = static function (int $size) use ($_): string {
 								<?php foreach ($_['navigation'] as $entry): ?>
 									<li data-id="<?php p($entry['id']); ?>">
 									<a href="<?php print_unescaped($entry['href']); ?>"
-										<?php if ($entry['target']): ?> target="_blank" rel="noreferrer noopener"<?php endif; ?>
+										<?php if (isset($entry['target']) && $entry['target']): ?> target="_blank" rel="noreferrer noopener"<?php endif; ?>
 										<?php if ($entry['active']): ?> class="active"<?php endif; ?>
 										aria-label="<?php p($entry['name']); ?>">
 										<svg width="20" height="20" viewBox="0 0 20 20" alt=""<?php if ($entry['unread'] !== 0) { ?> class="has-unread"<?php } ?>>