Fixed several instances in WordPress where PHP Notices are not being handled correctly.

Fixes supplied by Aaron Jensen (aaron@visualprose.com).


git-svn-id: http://svn.automattic.com/wordpress/trunk@559 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-settings.php

@@ -4,7 +4,7 @@
 // We should eventually migrate to either calling
 // get_settings() wherever these are needed OR
 // accessing a single global $all_settings var
-if (!$_wp_installing) {
+if (!isset($_wp_installing) || !$_wp_installing) {
     $siteurl = get_settings('siteurl');
 	// "When trying to design a foolproof system, 
 	//  never underestimate the ingenuity of the fools :)"