Web process errors when donation link for another steam ID is opened

[FlorianSW]

When I open a donation link (/donate/:donationId) of someone else (a donation not associated with my steam ID), then the following error occurs:

[21-08-21 04:08:38][error]    Unknown error SteamIdMismatch
[21-08-21 04:08:39][error]    middlewareError
Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:561:11)
    at ServerResponse.header (C:\Users\admin\Documents\server-donation-tool\node_modules\express\lib\response.js:771:10)
    at ServerResponse.send (C:\Users\admin\Documents\server-donation-tool\node_modules\express\lib\response.js:170:12)
    at done (C:\Users\admin\Documents\server-donation-tool\node_modules\express\lib\response.js:1008:10)
    at tryHandleCache (C:\Users\admin\Documents\server-donation-tool\node_modules\ejs\lib\ejs.js:278:5)
    at View.exports.renderFile [as engine] (C:\Users\admin\Documents\server-donation-tool\node_modules\ejs\lib\ejs.js:489:10)
    at View.render (C:\Users\admin\Documents\server-donation-tool\node_modules\express\lib\view.js:135:8)
    at tryRender (C:\Users\admin\Documents\server-donation-tool\node_modules\express\lib\application.js:640:10)
    at Function.render (C:\Users\admin\Documents\server-donation-tool\node_modules\express\lib\application.js:592:3)
    at ServerResponse.render (C:\Users\admin\Documents\server-donation-tool\node_modules\express\lib\response.js:1012:7)
    at errorHandler (C:\Users\admin\Documents\server-donation-tool\dist\logging.js:50:28)
    at newFn (C:\Users\admin\Documents\server-donation-tool\node_modules\express-async-errors\index.js:16:20)
    at Layer.handle_error (C:\Users\admin\Documents\server-donation-tool\node_modules\express\lib\router\layer.js:71:5)
    at trim_prefix (C:\Users\admin\Documents\server-donation-tool\node_modules\express\lib\router\index.js:315:13)
    at C:\Users\admin\Documents\server-donation-tool\node_modules\express\lib\router\index.js:284:7
    at Function.process_params (C:\Users\admin\Documents\server-donation-tool\node_modules\express\lib\router\index.js:335:12)

And the request is cancelled without a response. This should, however, trigger a proper error message.