Helm chart rendering fails since version 0.4.37

[Gerrit-K]

Describe the bug
The chart rendering fails since version 0.4.37 with the error:

Error: template: datahub/charts/datahub-mce-consumer/templates/deployment.yaml:347:31: executing "datahub/charts/datahub-mce-consumer/templates/deployment.yaml" at <.Values.global.datahub.metadataChangeProposal.consumer.batch.enabled>: nil pointer evaluating interface {}.consumer

To Reproduce
Steps to reproduce the behavior:

1. Render the Helm Chart
2. Observe the error

Expected behavior
The default values should not cause any rendering errors.

Additional context
Probably related to this PR where a flag .Values.global.datahub.metadataChangeProposal.consumer.batch.enabled was added to the mce-consumer without adding the default value to the subchart's values (like it was done for the gms in the same PR.