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/issue/filters.tmpl

@@ -1,6 +1,6 @@
 <div id="issue-filters" class="issue-list-toolbar">
 	<div class="issue-list-toolbar-left">
-		{{if and ($.CanWriteIssuesOrPulls) (gt (len .Issues) 0)}}
+		{{if and $.CanWriteIssuesOrPulls .Issues}}
 			<input type="checkbox" autocomplete="off" class="issue-checkbox-all gt-mr-4" title="{{ctx.Locale.Tr "repo.issues.action_check_all"}}">
 		{{end}}
 		{{template "repo/issue/openclose" .}}

templates/repo/issue/view_content/sidebar.tmpl

@@ -339,7 +339,7 @@
 				</div>
 			</div>
 		{{end}}
-		{{if gt (len .WorkingUsers) 0}}
+		{{if .WorkingUsers}}
 			<div class="divider"></div>
 			<div class="ui comments">
 				<span class="text"><strong>{{ctx.Locale.Tr "repo.issues.time_spent_from_all_authors" ($.Issue.TotalTrackedTime | Sec2Time) | Safe}}</strong></span>