Error in javascript when authenticating with Azure AD B2C, using MSAL on WinForms .NET Framework 4.8

Question

I'm using Azure AD B2C in a Windows Forms application (.NET Framework 4.8). When the MSAL library opens the embedded webview to authenticate the user, it shows the following error message:

The user flow is SignupSignin, version "Recommended" and the template is "Classic" without any customization.

Looking at the javascript, it seems related to this line:

r.catch(()=>{})}};