Index: plugins/user_relationship_invites/user_relationship_invites.module
===================================================================
--- plugins/user_relationship_invites/user_relationship_invites.module	(.../orig/current/sites/all/modules/user_relationships)	(revision 3357)
+++ plugins/user_relationship_invites/user_relationship_invites.module	(.../trunk/sites/all/modules/user_relationships)	(revision 3357)
@@ -95,11 +95,13 @@
 
   switch ($action) {
   case 'invite':
-    db_query(
-      "INSERT INTO {user_relationship_invites} (`inviter_uid`, `rtid`, `invite_code`) VALUES (%d, %d, '%s')", 
-      $args['inviter']->uid, $form_values['rtid'], $args['code']
-    );
+    if ($form_values['rtid']) {
+      db_query(
+        "INSERT INTO {user_relationship_invites} (inviter_uid, rtid, invite_code) VALUES (%d, %d, '%s')", 
+        $args['inviter']->uid, $form_values['rtid'], $args['code']
+      );
+    }
     break;
   }
 }
 
@@ -113,8 +118,8 @@
 
   switch($type) {
   case 'insert':
-    if (isset($edit['relationship_invite_approve'])) {
+    if (isset($edit['relationship_invite_approve']) && isset($edit['invite_code'])) {
       db_query("DELETE FROM {user_relationship_invites} WHERE invite_code = '%s'", $edit['invite_code']);
 
       if ($edit['relationship_invite_approve'] == 'approve') {

Index: user_relationships_api.inc
===================================================================
--- user_relationships_api.inc	(.../orig/current/sites/all/modules/user_relationships)	(revision 3357)
+++ user_relationships_api.inc	(.../trunk/sites/all/modules/user_relationships)	(revision 3357)
@@ -97,6 +97,24 @@
       $$key = $key == 'type' ? user_relationships_type_load($value) : user_load(array('uid' => $value));
     }
   }
+  if (!$requester) {
+    $msg = t('Invalid requester in relationship request');
+    drupal_set_message($msg);
+    error_log($msg);
+    return;
+  }
+  if (!$requestee) {
+    $msg = t('Invalid requestee in relationship request');
+    drupal_set_message($msg);
+    error_log($msg);
+    return;
+  }
+  if (!$type) {
+    $msg = t('Invalid type in relationship request');
+    drupal_set_message($msg);
+    error_log($msg);
+    return;
+  }
 
   //Enforce the single relationship restriction, also http://drupal.org/node/271247
   if (!variable_get('user_relationships_allow_multiple', TRUE)) {