CSS: Hide collapsed sections when JS is disabled

What is wrong with the collapse_api semantics:
JS writes the collapse state in a cookie; the server retrieves it to
display each section in the proper state. The classes 'collapse_closed'
and 'collapse_open' may be reversed, causing a collapsed section to have
class 'collapse_open'... wtf?

This commit fixes the problem by creating a new class to identify which
section is the collapsed one. This new class is not affected by
javascript, and hidden by default using CSS.

Fixes #19508

Signed-off-by: Damien Regad <dregad@mantisbt.org>

Changes from cproensa's original commits:
- squashed
- commit message reworded
- CSS rule on a single line

core/collapse_api.php

@@ -110,7 +110,7 @@ function collapse_closed( $p_name, $p_section = '' ) {
 	ob_start();
 
 	$t_div_id = $t_block . '_closed';
-	echo "\n<div id=\"", $t_div_id, '"', ( $t_display ? ' class="collapse-open"' : ' class="collapse-closed"' ), '>';
+	echo "\n<div id=\"", $t_div_id, '" class="collapse-section-closed ', ( $t_display ? 'collapse-open' : 'collapse-closed' ), '">';
 }
 
 /**

css/default.css

@@ -804,3 +804,6 @@ div.timeline * div.action { padding-top: 3px; }
 /* bug_view_inc bug action buttons */
 .details-footer      { padding: 3px 10px 2px 0; }
 .details-buttons     { float: left;  width: auto; }
+
+/* Hide collapsed sections for javascript disabled presentation  */
+.collapse-section-closed { display: none; }