Entering a repeated or non-existent node to Add a Dependency Panel should fail or not change the graph

[NightLore]

• Repeated nodes should not change the graph, maybe indicate somewhere that it is repeated?
  • ideally this indication should show where the repeat is
• non-existent libraries should either create a "Failed to Load" node or indicate somewhere that it does not exist
  • if just using indication, could put an error text above the Add Dependency Panel