YAML missing anchor prevents changes to dynamic definition being saved

[philayres]

The following scenario causes an error that is difficult to recover from. As an admin, I:

• create a new dynamic model
• add options that include a YAML anchor and subsequently use it with an alias
• save the dynamic model
• continue editing and delete the YAML anchor
• save the changes

An error appears, due to the missing anchor. The problem is, even if I add in the anchor to the options, I'm unable to save the definition, since the same error keeps on appearing.

[philayres]

Fixed by 039f47e