Description of problem:
During the creation of ROSA Classic cluster via UI wizard, Under machine pool step, user specified node label key and value then added additional key and value field using "add additional label". User tries to move to next step without any value in both key and value field.
No validation is thrown against the field also user not allowed to proceed to next step. It create confusions and we need to throw validation error in above situation.
Note : The behavior works fine with OSD wizard and fails only in ROSA.

See the recordings ValidationErrorLabel.mp4

How reproducible:
always

Steps to Reproduce:

1. Open OCM UI staging.
2. Open ROSA Classic cluster wizard.(choose control plane as "Classic")
3. Fill all required fields and reach to machine pool step.
4. Expand "Edit node labels" option and fill the key and value fields.
5. Click "Add additional label" (Do not enter anything or do nothing)
6. Click "Next" button and view the behavior.

Actual results:
At Step 6, User neither taken to next step nor thrown validation error against empty fields. 

Expected results:
At step 6, the validation error message should throw against the empty key field for the label.