Problem description: In web scenario step configuration form, empty row in variables field are considered eligible during variable name uniqueness validation, therefore, if a web scenario step has more than 1 empty row in Variables table, then saving its' configuration will fail with the following error:

Incorrect value for field "variables/2": value (name)=() already exists.

Steps to reproduce:

1. Open any existing web scenario configuration in edit mode
2. Move to Steps tab and press Add button in Steps field
3. In the opened form fill in the name and URL
4. Make sure that there are two empty rows in the "Variables" field table
5. Attempt to save step configuration

Result: the above error is returned
Expected: empty rows in Variables table should be removed before validating their uniqueness, or should not be considered eligible for this check.

Example: