Issue #3202814 by attiks: Allow array of strings to be mapped

src/ExternalEntityStorage.php

@@ -307,8 +307,15 @@ class ExternalEntityStorage extends ContentEntityStorageBase implements External
           if (!empty($raw_data[$exploded_mapped_key[0]]) && isset($exploded_mapped_key[1]) && $exploded_mapped_key[1] === '*') {
             $parents = array_slice($exploded_mapped_key, 2);
             foreach (array_values($raw_data[$exploded_mapped_key[0]]) as $key => $value) {
+              $is_an_array = is_array($value);
               $value = !is_array($value) ? [$value] : $value;
-              $field_values[$key][$property_name] = NestedArray::getValue($value, $parents);
+
+              if ($is_an_array) {
+                $field_values[$key][$property_name] = NestedArray::getValue($value, $parents);
+              }
+              else {
+                $field_values[$key][$property_name] = reset(NestedArray::getValue($value, $parents));
+              }
             }
           }
           else {