[FIX] web_editor: bg-transparent filter=>no opaque

The color picker in snippet options has two way to set a color: have a
data-color attribute => it is used, or have a o_custom_color class and
the background-color is set directly on that color.

In the case where we select no background color (transparent), it would
work in preview, but when applied the opaque color of the transparent
button (since opacity is not copied) is set which is wrong and
unexpected.

opw-2053636
closes #36131

Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>

addons/web_editor/static/src/js/editor/snippets.options.js

@@ -770,7 +770,7 @@ registry.colorpicker = SnippetOption.extend({
         if ($selected.length) {
             if ($selected.data('color')) {
                 this.$target.addClass(this.colorPrefix + $selected.data('color'));
-            } else {
+            } else if ($selected.hasClass('o_custom_color')) {
                 this.$target.css('background-color', $selected.css('background-color'));
             }
         }