Fix noneffective static variable cache in log_message()
diff --git a/system/core/Common.php b/system/core/Common.php
index 28c6083..98a3fcb 100644
--- a/system/core/Common.php
+++ b/system/core/Common.php
@@ -453,10 +453,11 @@
 
 		if ($_log === NULL)
 		{
-			$_log =& load_class('Log', 'core');
+			// references cannot be directly assigned to static variables, so we use an array
+			$_log[0] =& load_class('Log', 'core');
 		}
 
-		$_log->write_log($level, $message, $php_error);
+		$_log[0]->write_log($level, $message, $php_error);
 	}
 }