ture 1514: improvement, impossible to activate a theme is a parent is missing

(a parent includes grand father and his own father, and his own father, and so
on... until the root theme is "default" or has no parent declared)

git-svn-id: http://piwigo.org/svn/trunk@5259 68402e56-0260-453c-a942-63ccdbb3a9ee

admin/themes/default/template/themes_installed.tpl

@@ -33,13 +33,21 @@
     <div class="themeName">{$theme.name}</div>
     <div class="themeShot"><img src="{$theme.screenshot}"></div>
     <div class="themeActions">
+
+  {if $theme.activable}
       <a href="{$activate_baseurl}{$theme.id}" title="{'Make this theme available to users'|@translate}">{'Activate'|@translate}</a>
+  {else}
+      <span title="{$theme.activate_tooltip}">{'Activate'|@translate}</span>
+  {/if}
+
       |
+
   {if $theme.deletable}
       <a href="{$delete_baseurl}{$theme.id}" onclick="return confirm('{'Are you sure?'|@translate|@escape:javascript}');" title="{'Delete this theme'|@translate}">{'Delete'|@translate}</a>
   {else}
       <span title="{$theme.delete_tooltip}">{'Delete'|@translate}</span>
   {/if}
+
     </div>
     
   </div>