Only close the session if it had been opened.

boot.php

@@ -1698,7 +1698,9 @@ function login($register = false, $hiddens=false) {
  * @brief Used to end the current process, after saving session state.
  */
 function killme() {
-	session_write_close();
+	if (!get_app()->is_backend())
+		session_write_close();
+
 	exit;
 }
 

index.php

@@ -489,7 +489,8 @@ if (isset($_GET["mode"]) AND ($_GET["mode"] == "raw")) {
 
 	echo substr($target->saveHTML(), 6, -8);
 
-	session_write_close();
+	if (!$a->is_backend())
+		session_write_close();
 	exit;
 
 }
@@ -514,5 +515,6 @@ if(!$template) {
 
 require_once($template);
 
-session_write_close();
+if (!$a->is_backend())
+	session_write_close();
 exit;

mod/hostxrd.php

@@ -25,7 +25,6 @@ function hostxrd_init(&$a) {
 		'$zot_post' => z_root() . '/post',
 		'$bigkey' => salmon_key(get_config('system','site_pubkey')),
 	));
-	session_write_close();
 	exit();
 
 }