Problem description : When configuring a webhook media type, space is accepted as a valid value of the following fields:

• Parameters -> Name
• Script
• Menu entry name

Correct me if I'm wrong, but I don't see how to properly use a webhook with script field equal to just a blank space, a webhook parameter with a blank space as parameter name, or a menu entry with a blank space as a name.

Steps to reproduce:

1. Navigate to Administration => Media types and press "Create media type"
2. Specify the name of the media type and set field "Type" to "Webhook"
3. Add a new parameter to the media type - use a blank space as the name of the parameter.
4. Use a blank space as the value of field "Script".
5. Set "Include entry name" to true and specify a valid URL in "Menu entry URL"
6. Use a blank space as the value of the "Menu entry name".
7. Attempt to save the created media type.

Result: Media type successfully created

Expected: Using a blank space as the value of the above mentioned fields should not be allowed.

Example: