Issue #3028162: Added a test for multiple values.

Closes #3028162

src/Plugin/migrate_plus/data_parser/SimpleXml.php

@@ -75,7 +75,7 @@ class SimpleXml extends DataParserPluginBase {
       foreach ($this->fieldSelectors() as $field_name => $xpath) {
         foreach ($target_element->xpath($xpath) as $value) {
           if ($value->children() && !trim((string) $value)) {
-            $this->currentItem[$field_name] = $value;
+            $this->currentItem[$field_name][] = $value;
           }
           else {
             $this->currentItem[$field_name][] = (string) $value;