Juju GUI not managing bundle import properly

Hello,

I noticed the bundles that are exported by the GUI are now different from what they used to be. They now contain the list of machines along with constraints at the machine level, not the service level.

However, the bundles in the store itself do not contain this information (machines are not in the yaml file)

* When deploying a bundle from the store, there is an additional step (commit) to take to really deploy, that was not needed in the past
* But when drag'n'dropping a bundle or using import button:
  * if the bundle was exported by the current GUI, with machines references, it deploys OK
  * if format in the charm store or previous bundles (without machine constraints), the deployment fails and the GUI says

Error generating changeSet

There was an error generating the changeSet. See browser console for additional information

The console itself says:
Error: Invalid value for <g> attribute transform="translate(undefined,undefined)"

To reproduce:
* Take any bundle in the store and deploy + commit deployment.
* Then export
* Then edit the yaml file to remove the machines that are listed, and remove the "to: XXX" in service description.
* Then try to import again.

Some bundles that would also fail are available here : https://github.com/SaMnCo/bundle-sentiment-analysis