Fixed page slug generation on the admin side.

app/views/admin/page/editor.pug

@@ -18,11 +18,13 @@ block content
           label(for="slug").uk-form-label URL slug
           -
             var pageSlug;
-            pageSlug = page ? (page.slug || 'enter-slug-here').split('-') : ['enter', 'slug', 'here', ''];
-            pageSlug.pop();
-            pageSlug = pageSlug.join('-');
+            if (page) {
+              pageSlug = page.slug.split('-');
+              pageSlug.pop();
+              pageSlug = pageSlug.join('-');
+            }
           input(id="slug", name="slug", type="text", placeholder= "Enter page URL slug", value= page ? pageSlug : undefined).uk-input
-          .uk-text-small The slug is used in the link to the page https://#{site.domain}/page/#{pageSlug}
+          .uk-text-small The slug is used in the link to the page https://#{site.domain}/page/#{page ? page.slug : 'your-slug-here'}
         div(uk-grid)
           .uk-width-auto
             button(type="submit").uk-button.dtp-button-primary= page ? 'Update page' : 'Create page'