message: fix(protocol-designer): fix bug with selecting magnet > disengage step
  Closes
diff: @@ -142,7 +142,7 @@ export const selectStep = (
  }
  // auto-select magnetic module if it exists (assumes no more than 1 magnetic module)
  - if (formData && formData.stepType === 'magnet') {
  + if (newStepType === 'magnet') {
  const moduleId = uiModulesSelectors.getSingleMagneticModuleId(state)
  const magnetAction = getNextDefaultMagnetAction(
  stepFormSelectors.getSavedStepForms(state),
  @@ -166,6 +166,11 @@ export const selectStep = (
  // recommended value is null when no labware found on module
  const engageHeight = prevEngageHeight || stringDefaultEngageHeight
  formData = { ...formData, moduleId, magnetAction, engageHeight }
  + } else if (formData?.stepType === 'magnet') {
  + // handle case for pristine-never-saved Magnet step:
  + // it needs the moduleId field populated, bc that field has no UI
  + const moduleId = uiModulesSelectors.getSingleMagneticModuleId(state)
  + formData = { ...formData, moduleId }
  }
  dispatch({
  