[2.7] ACM ignores Policies about empty label/field

Description of problem:

Wen create a policy to set some empty labels, like:

      - complianceType: musthave
          objectDefinition:
            apiVersion: v1
            kind: Node
            metadata:
              labels:
                cluster.ocs.openshift.io/openshift-storage: ""               
                node-role.kubernetes.io/worker: ""  
                node-role.kubernetes.io/role2: ""
              name: master-0

This is ignored. It seems to be related to that empty label, that is used to add an extra role to a Node object.

The policy appears as compliant, when it is not.

Version-Release number of selected component (if applicable):

2.7

How reproducible:

Create a policy that sets some empty fields, like a role for a Node.

Steps to Reproduce:

1.  
2.  
3. ...

Actual results:

The Policy appears as compliance. But this has not be applied, and the empty fields (roles) have not been added. You cannot enforce the Policy because it is set as compliance, when is not.

Expected results:

Additional info: