=== modified file 'dhis-2/dhis-services/dhis-service-core/src/main/java/org/hisp/dhis/validation/DefaultValidationRuleService.java'
--- dhis-2/dhis-services/dhis-service-core/src/main/java/org/hisp/dhis/validation/DefaultValidationRuleService.java	2013-04-22 15:12:36 +0000
+++ dhis-2/dhis-services/dhis-service-core/src/main/java/org/hisp/dhis/validation/DefaultValidationRuleService.java	2013-04-22 15:25:38 +0000
@@ -292,7 +292,7 @@
                             {
                                 violation = ( leftSide != null && rightSide == null ) || ( leftSide == null && rightSide != null );
                             }
-                            else
+                            else if ( leftSide != null && rightSide != null )
                             {
                                 violation = !expressionIsTrue( leftSide, operator, rightSide );
                             }