Index: branches/RC/core/units/general/helpers/themes_helper.php
===================================================================
diff -u -N -r11682 -r11830
--- branches/RC/core/units/general/helpers/themes_helper.php	(.../themes_helper.php)	(revision 11682)
+++ branches/RC/core/units/general/helpers/themes_helper.php	(.../themes_helper.php)	(revision 11830)
@@ -345,7 +345,13 @@
 			}
 
 			// use current theme, because it's available on Front-End
-			return $this->Application->GetVar('m_theme');
+			$theme_id = $this->Application->GetVar('m_theme');
+			if (!$theme_id) {
+				// happens in mod-rewrite mode, then requested template is not found
+				$theme_id = $this->Application->GetDefaultThemeId();
+			}
+
+			return $theme_id;
 		}
 
 		/**