feat: allow card without cover img (even without default cover)

layout/_index_style/card.ejs

@@ -6,21 +6,24 @@
             </div>
         <% } %>
         <div class="kratos-entry-post-main">
-            <div class="kratos-entry-thumb">
-                <a href="<%- url_for(post.path) %>">
-                    <img class="kratos-entry-thumb-img" src="<%- 
-                        post.cover ? (
-                            /^(#|\/\/|http(s)?:)/.test(post.cover) ? 
-                            post.cover : 
-                            url_for(
-                                post.cover.startsWith('/') ? 
-                                post.cover : 
-                                post.path.replace(/(\/index)?\.html?$/, '') + '/' + post.cover
-                            )
-                        ) : theme.posts.default_cover
-                    %>" alt="<%- url_for(post.title) %>">
-                </a>
-            </div>
+            <% let cover = post.cover === undefined ? theme.posts.default_cover : (
+                post.cover ? (
+                    /^(#|\/\/|http(s)?:)/.test(post.cover) ? 
+                    post.cover : 
+                    url_for(
+                        post.cover.startsWith('/') ? 
+                        post.cover : 
+                        post.path.replace(/(\/index)?\.html?$/, '') + '/' + post.cover
+                    )
+                ) : null
+            ); %>
+            <% if (cover) { %>
+                <div class="kratos-entry-thumb">
+                    <a href="<%- url_for(post.path) %>">
+                        <img class="kratos-entry-thumb-img" src="<%- cover %>" alt="<%- url_for(post.title) %>">
+                    </a>
+                </div>
+            <% } %>
             <div class="kratos-entry-post-inner">
                 <header class="kratos-entry-header">
                         <%- list_categories(post.categories, {