Upload file error after upgrade

when I click the link to upload an attachment to a media gallery, the modal popup gives me this error:

Server Error in '/' Application.
Compilation Error
Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately.

Compiler Error Message: CS0234: The type or namespace name 'Controls' does not exist in the namespace 'Telligent.Evolution.MediaGalleries' (are you missing an assembly reference?)

Source Error:


Line 1: <%@ Page EnableViewState="false" Language="C#" AutoEventWireup="true" MasterPageFile="~/modals/modal.Master" %>
Line 2: <%@ Register TagPrefix="TEMedia" Namespace="Telligent.Evolution.MediaGalleries.Internal.Legacy.Controls.Forms" Assembly="Telligent.Evolution.MediaGalleries" %>
Line 3:
Line 4: <asp:Content ContentPlaceHolderID="content" runat="server">

Source File: g:\Telligent12\T12-Base\Web\modals\media\uploadpostattachment.aspx Line: 2


Show Detailed Compiler Output:


Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.7.3701.0