Description of problem:
Clicking multiple times on the event source type in the event source form will toggle the create button enablement even when the form is invalid.

Prerequisites (if any, like setup, operators/versions):
install knative serverless operator

Steps to Reproduce
1. go to add => event sources
2. Select a type
3. Click the same type again

Actual results:
Create button becomes enabled. Clicking the same type again toggles the create button enablement between disabled and enabled.

Expected results:
Create button should remain disabled until form is valid.

Reproducibility (Always/Intermittent/Only Once):
always

Build Details:
4.6.0-0.nightly-2020-07-07-233934