[FIX] website_blog: more tolerant with cover property

resize_class can be missing from the properties

opw-2379828

closes odoo/odoo#61786

Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>

addons/website_blog/views/website_blog_templates.xml

@@ -241,7 +241,7 @@ list of filtered posts (by date or tag).
                             <div t-field="blog_post.name" id="o_wblog_post_name" class="o_editable_no_shadow" data-oe-expression="blog_post.name" t-att-data-blog-id="blog_post.id" placeholder="Blog Post Title"/>
                             <div t-field="blog_post.subtitle" id="o_wblog_post_subtitle" class="o_editable_no_shadow" placeholder="Subtitle"/>
                         </div>
-                        <t t-set="resize_classes" t-value="set(json.loads(_record.cover_properties).get('resize_class').split(' '))"/>
+                        <t t-set="resize_classes" t-value="set(json.loads(_record.cover_properties).get('resize_class', '').split(' '))"/>
                         <a t-if="{'o_full_screen_height', 'o_half_screen_height', 'cover_full', 'cover_mid'}.intersection(resize_classes)"
                             id="o_wblog_post_content_jump" href="#o_wblog_post_main"
                             class="css_editable_mode_hidden justify-content-center align-items-center rounded-circle mx-auto mb-5 text-decoration-none">