Refactor template empty checks (#28351) (#28354)

Backport #28351 by @KN4CK3R

Fix #28347

As there is no info how to reproduce it, I can't test it.
Fix may be `section_split.tmpl @ 126/130`.

Other changes are "empty check" refactorings.

Co-authored-by: KN4CK3R <admin@oldschoolhack.me>

templates/user/notification/notification_div.tmpl

@@ -24,7 +24,7 @@
 		</div>
 		<div class="gt-p-0">
 			<div id="notification_table">
-				{{if eq (len .Notifications) 0}}
+				{{if not .Notifications}}
 					<div class="gt-df gt-ac gt-fc gt-p-4">
 						{{svg "octicon-inbox" 56 "gt-mb-4"}}
 						{{if eq .Status 1}}

templates/user/notification/notification_subscriptions.tmpl

@@ -63,7 +63,7 @@
 					</div>
 				</div>
 				<div class="divider"></div>
-				{{if eq (len .Issues) 0}}
+				{{if not .Issues}}
 					{{ctx.Locale.Tr "notification.no_subscriptions"}}
 				{{else}}
 					{{template "shared/issuelist" dict "." . "listType" "dashboard"}}