Property test failure

[Gabriella439]

With some seeds the tests fail with an error like this:

Failures:

  tests/Data/GraphVizSpec.hs:29:3: 
  1) Data.GraphViz Ensure augmentation is valid
       uncaught exception: ErrorCall
       Map.!: given key is not an element in the map
       CallStack (from HasCallStack):
         error, called at libraries/containers/containers/src/Data/Map/Internal.hs:617:17 in containers-0.6.7:Data.Map.Internal
       (after 106 tests and 1 shrink)
         mkGraph [(-2,'e'),(1,'=')] [(-2,1,-1.0),(1,-2,-1.0)]

  To rerun use: --match "/Data.GraphViz/Ensure augmentation is valid/"

Randomized with seed 57347323