Rendered entity tooltip only works for nodes

Problem/Motivation

When creating a Leaflet map view where the rendered entity type is not "node" and using the rendered entity tooltip option, the site throws a fatal exception:

Error: Call to a member function getEntityTypeId() on null in Drupal\leaflet_views\Plugin\views\style\LeafletMap->render() (line 421 of modules/contrib/leaflet/leaflet_views/src/Plugin/views/style/LeafletMap.php).

This is why the current code has a hardcoded referenced to "nid" property.
$entity = $this->entityManager->getStorage($this->entityType)->load($result->nid);
So when the view is rendering a different entity type IE: user, fails.

Proposed resolution

Refactor that piece of code to make it work with any entity type.

Remaining tasks

Provide patch
Pass QA

User interface changes

None

API changes

None

Data model changes

None