update public/install.php.

安装文件修复bug

public/install.php

@@ -676,11 +676,11 @@ function show_msg($msg, $class = 'primary'){
 	ob_flush();
 }
 
-function session($name, $value = false){
+function session($name, $value = ''){
 	if ($name == '') {
 		return false;
 	}
-	if (false !== $value) {
+	if ('' !== $value) {
 		$_SESSION[$name] = $value;
 	}else{
 		return isset($_SESSION[$name]) ? $_SESSION[$name] : false;