helpers: tls detection fix by adding default dict

Address #1653 (closed) by adding a (default (dict) x ) around global.ingress.tls as the behavior surrounding this line changed in Helm 2.15.x.

This change restores the expected behavior as experienced with Helm 2.14.x

Closes #1653 (closed)

See 1653, specifically:

The simplest method appears to be populating global.ingress.tls: {}, but this actually requires deeper testing.

Instead, I'm going to suggest we update the gitlab.ingress.tls.configured template, with $global := pluck "secretName" (default (dict) $.Values.global.ingress.tls) | first, which will restore the existing behavior.