Interrapt G21

Description
Webinar can be created with end date that is before the start date
Steps to reproduce:
1. Open Webinars page
2. Click Create button
3. Fill in Title and description fields
4. Choose todays date for start date
5. Choose yesterdays date for end date
6. Select image, mentor and tag
7. Click Create button

Expected result:
When choosing the end date, there should be a message in red letters saying that the field must be filled in correctly

Actual result:
The user creates the webinar successfully