This only triggers on a dev build, because apparently we don't check the invariant on compareRelationships elsewhere. To reproduce:

1) Go to /work/create?rels.0.target=d3dd86df-2f57-4a97-8100-d09915343f60 (works with sample data)
2) Click the + button by the "no type" relationship that was seeded
3) Add a different relationship (for example, select "writer" and "Diamond Head" again, but AFAICT it happens with any choice

The following error is returned:
Oops, something went wrong!
Error: Invariant Violation
at invariant (http://reolappy:5000/static/build/common-chunks.js:85066:11)
at compareRelationships (http://reolappy:5000/static/build/common-chunks.js:80420:5)
at compareBackwardRelationships (http://reolappy:5000/static/build/common-chunks.js:80481:10)
at remove (http://reolappy:5000/static/build/common-chunks.js:131858:15)
at updateLinkPhraseGroup (http://reolappy:5000/static/build/common-chunks.js:82930:32)
at Module.update (http://reolappy:5000/static/build/common-chunks.js:132172:26)
at updateLinkTypeGroup (http://reolappy:5000/static/build/common-chunks.js:82954:86)
at Module.update (http://reolappy:5000/static/build/common-chunks.js:132172:26)
at updateTargetTypeGroup (http://reolappy:5000/static/build/common-chunks.js:82978:88)
at Module.update (http://reolappy:5000/static/build/common-chunks.js:132172:26)