Test Plan filters returns error when filtering by "without" Test Environments without selecting an Environment

Short Description: When opening the Test Plan filters and picking the option filter "without" Test Environments and immediately pressing "Apply", an error is returned stating that "Tests can not be added to Test Plan because body (environment): invalid value". 

Steps to Reproduce:

1 - Navigate to a Test Plan with Tests on it

2 - Open the Test Plan filters

3 - Select "without" and press "Apply" button

Actual Result: An error message is displayed

Expected Result: No error message should be displayed. In this case system should assume all tests, as it does for the option "with"