Dashboard: Unable to add or remove companies to an event

[juliangra]

Bug description
Currently, members trying to add and/or remove companies from the list of companies attending an event are unable to do so, as you are redirected to an error 404 page.

To Reproduce
Steps to reproduce the behavior:

1. Go to the dashboard and create a new event
2. Click on the "Bedrifter" tab
3. Select a company from the dropdown list
4. Click "Lagre"
5. See that the company name is not visible, but a "Fjern" button has appeared
6. Upon clicking the "Fjern" button, you are redirected to an error 404 page.

Expected behavior
The expected behavior is that the name of the company added will be displayed alongside the "Fjern" button and that pressing the button will remove the company from the list of attending companies.

Desktop (please complete the following information):

• OS: macOS Big Sur 11.0.1
• Browser: Chrome
• Version: 88.0.4324.96