3 files changed, 32 insertions, 1 deletions
diff --git a/admin/include/themes.class.php b/admin/include/themes.class.php
index 86651f55f..524462306 100644
--- a/admin/include/themes.class.php
+++ b/admin/include/themes.class.php
@@ -117,6 +117,16 @@ INSERT INTO ".THEMES_TABLE."
           break;
         }
 
+        // you can't deactivate the last theme
+        if (count($this->db_themes_by_id) <= 1)
+        {
+          array_push(
+            $errors,
+            l10n('Impossible to deactivate this theme, you need at least one theme.')
+            );
+          break;
+        }
+
         if ($theme_id == get_default_theme())
         {
           // find a random theme to replace
@@ -227,6 +237,8 @@ DELETE
 
   function set_default_theme($theme_id)
   {
+    global $conf;
+    
     // first we need to know which users are using the current default theme
     $default_theme = get_default_theme();
     
@@ -236,7 +248,12 @@ SELECT
   FROM '.USER_INFOS_TABLE.'
   WHERE theme = "'.$default_theme.'"
 ;';
-    $user_ids = array_from_query($query, 'user_id');
+    $user_ids = array_unique(
+      array_merge(
+        array_from_query($query, 'user_id'),
+        array($conf['guest_id'], $conf['default_user_id'])
+        )
+      );
 
     // $user_ids can't be empty, at least the default user has the default
     // theme
diff --git a/admin/themes/default/template/themes_installed.tpl b/admin/themes/default/template/themes_installed.tpl
index 28d4df66a..5bb18ae57 100644
--- a/admin/themes/default/template/themes_installed.tpl
+++ b/admin/themes/default/template/themes_installed.tpl
@@ -13,7 +13,13 @@
     <div class="themeName">{$theme.name}{if $theme.is_default} <em>({'default'|@translate})</em>{/if}</div>
     <div class="themeShot"><img src="{$theme.screenshot}"></div>
     <div class="themeActions">
+
+{if $theme.deactivable}
       <a href="{$deactivate_baseurl}{$theme.id}" title="{'Forbid this theme to users'|@translate}">{'Deactivate'|@translate}</a>
+{else}
+      <span title="{$theme.deactivate_tooltip}">{'Deactivate'|@translate}</span>
+{/if}
+      
 {if not $theme.is_default}
       | <a href="{$set_default_baseurl}{$theme.id}" title="{'Set as default theme for unregistered and new users'|@translate}">{'Default'|@translate}</a>
 {/if}
diff --git a/admin/themes_installed.php b/admin/themes_installed.php
index dda2ab6ed..7ef26ead7 100644
--- a/admin/themes_installed.php
+++ b/admin/themes_installed.php
@@ -77,6 +77,14 @@ foreach ($themes->fs_themes as $theme_id => $fs_theme)
 
   if (in_array($theme_id, $db_theme_ids))
   {
+    $fs_theme['deactivable'] = true;
+    
+    if (count($db_theme_ids) <= 1)
+    {
+      $fs_theme['deactivable'] = false;
+      $fs_theme['deactivate_tooltip'] = l10n('Impossible to deactivate this theme, you need at least one theme.');
+    }
+    
     if ($theme_id == $default_theme)
     {
       $fs_theme['is_default'] = true;