Error: Call to a member function getEntityType() on null

INTRO:
I end up to install this module because I was looking for a way to display (in a view) a field and its translation.
I asked this question in stackoverflow (https://drupal.stackexchange.com/questions/261523/how-to-create-a-view-t...) and someone answered by linking to this module.

The bug is easy to explain:

1-Install the module
2-clear the caches to get those errors:

Notice: Undefined index: entity_id in Drupal\translate_side_by_side\Form\SettingsForm->buildFormMenu() (line 295 of modules/contrib/translate_side_by_side/src/Form/SettingsForm.php).
Drupal\translate_side_by_side\Form\SettingsForm->buildFormMenu(Array, Object, 'fr') (Line: 72)
Drupal\translate_side_by_side\Form\SettingsForm->buildForm(Array, Object)

Warning: array_flip(): Can only flip STRING and INTEGER values! in Drupal\Core\Entity\EntityStorageBase->getFromStaticCache() (line 139 of core/lib/Drupal/Core/Entity/EntityStorageBase.php).
Drupal\Core\Entity\EntityStorageBase->getFromStaticCache(Array) (Line: 231)
Drupal\Core\Entity\EntityStorageBase->loadMultiple(Array) (Line: 212)
Drupal\Core\Entity\EntityStorageBase->load(NULL) (Line: 296)
Drupal\translate_side_by_side\Form\SettingsForm->buildFormMenu(Array, Object, 'fr') (Line: 72)
Drupal\translate_side_by_side\Form\SettingsForm->buildForm(Array, Object)

3-Go to /admin/reports/translate_side_by_side to get this error:

Error: Call to a member function getEntityType() on null in Drupal\translate_side_by_side\Form\SettingsForm->buildFormMenu() (line 297 of modules/contrib/translate_side_by_side/src/Form/SettingsForm.php).
Drupal\translate_side_by_side\Form\SettingsForm->buildFormMenu(Array, Object, 'fr') (Line: 72)
Drupal\translate_side_by_side\Form\SettingsForm->buildForm(Array, Object)