Set encoding to UTF-8 when it is not specified.

Signed-off-by: Duncan Cameron <3147688+bramley@users.noreply.github.com>

Author: bramley

src/Reader/Reader.php

@@ -363,6 +363,9 @@ public static function importString($string)
         $disableEntityLoaderFlag = self::disableEntityLoader();
         $dom                     = new DOMDocument();
         $status                  = $dom->loadXML(trim($string));
+        if ($dom->encoding === null) {
+            $dom->encoding = 'UTF-8';
+        }
         foreach ($dom->childNodes as $child) {
             if ($child->nodeType === XML_DOCUMENT_TYPE_NODE) {
                 throw new Exception\InvalidArgumentException(