Index: trunk/core/kernel/utility/filters.php
===================================================================
diff -u -r1560 -r1980
--- trunk/core/kernel/utility/filters.php	(.../filters.php)	(revision 1560)
+++ trunk/core/kernel/utility/filters.php	(.../filters.php)	(revision 1980)
@@ -51,7 +51,7 @@
 			{
 				$this->filters[$name] = $clause->getSQL();	
 			}
-			elseif( !is_object($clause) && $clause )
+			elseif( !is_object($clause) && strlen($clause) )
 			{
 				$this->filters[$name] = $clause;
 			}