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/repo/actions/runs_list.tmpl

@@ -1,5 +1,5 @@
 <div class="flex-list">
-	{{if eq (len .Runs) 0}}
+	{{if not .Runs}}
 	<div class="empty-placeholder">
 		{{svg "octicon-no-entry" 48}}
 		<h2>{{if $.IsFiltered}}{{ctx.Locale.Tr "actions.runs.no_results"}}{{else}}{{ctx.Locale.Tr "actions.runs.no_runs"}}{{end}}</h2>