disabling voipnode behavior on one content type breaks other types marked as voipnode

Process to recreate:

1. Create content type A and check off "use this content type as a voip node"
2. Create content type B and check off "use this content type as a voip node"
3. Edit content type A and uncheck "use this content type as a voip node"

Bugs Observed:

• Editing cotent type B now shows an error saying "This content type has inactive fields. Inactive fields are not included in lists of available fields until their modules are enabled." (see attachment)
• Attempts to call voip functions, such as voipnode_get_greeting fail

Hypothesis:
I think what is happening is that when you uncheck a type as voipnode, it is disabling the shared adesc, agreet, etc fields. So type B can't use them.