'Inline' layouts page to check if a Site Collection exists

CheckIfSiteExists.aspx

<%@ Assembly Name="Microsoft.SharePoint.ApplicationPages, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c"%>
<%@ Assembly Name="Microsoft.SharePoint, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c"%>
<%@ Assembly Name="Microsoft.SharePoint.IdentityModel, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c"%>
<%@ Import Namespace="Microsoft.SharePoint" %>
<%@ Page Language="C#" AutoEventWireup="true" Inherits="Microsoft.SharePoint.IdentityModel.Pages.IdentityModelSignInPageBase" %>

<script runat="server" type="text/C#">
    protected void Page_Init(object sender, EventArgs e)
    {
        try
        {
            string site = Request.Params["Site"];

            using (SPSite spsite = new SPSite(site))
            {
                Response.Write(true);
            }
        }
        catch
        {
            Response.Write("false");
        }
        finally
        {
            Response.End();
        }
    }
</script>