diff -Naur drupal-7.15/includes/database/sqlite/query.inc drupal-7.15.patched/includes/database/sqlite/query.inc
--- drupal-7.15/includes/database/sqlite/query.inc      2012-08-01 16:27:42.000000000 +0000
+++ drupal-7.15.patched/includes/database/sqlite/query.inc      2012-09-08 20:43:23.000000000 +0000
@@ -72,11 +72,13 @@
    */
   protected function removeFieldsInCondition(&$fields, QueryConditionInterface $condition) {
     foreach ($condition->conditions() as $child_condition) {
-      if ($child_condition['field'] instanceof QueryConditionInterface) {
-        $this->removeFieldsInCondition($fields, $child_condition['field']);
-      }
-      else {
-        unset($fields[$child_condition['field']]);
+      if (isset($child_condition['field'])) {
+        if ($child_condition['field'] instanceof QueryConditionInterface) {
+          $this->removeFieldsInCondition($fields, $child_condition['field']);
+        }
+        else {
+          unset($fields[$child_condition['field']]);
+        }
       }
     }
   }
