message: fix(protocol-designer): ensure pipettes are removed from step forms when nuked
  We are changing the saved step forms when you edit your pipettes, the intended behavior included
  updating the removed pipette references to null, although that action was not being dispatched if a
  mount was set to null from a previously used mount.
diff: @@ -32,7 +32,7 @@ export const editPipettes = (payload: EditPipettesFields) =>
  const nextPipetteModel = pipetteFields.pipetteModel
  const nextTiprackModel = isEmpty(pipetteFields.tiprackModel) ? null : pipetteFields.tiprackModel
  const nextPipette: ?PipetteData = nextPipetteModel ? createPipette(mount, nextPipetteModel, nextTiprackModel) : null
  - return nextPipette ? {...acc, [mount]: nextPipette} : acc
  + return {...acc, [mount]: nextPipette}
  },
  {}
  )
  