cast institute name to string

Closes #1076

Merge request studip/studip!643

lib/classes/JsonApi/Schemas/Institute.php

@@ -22,7 +22,7 @@ class Institute extends SchemaProvider
     public function getAttributes($institute, ContextInterface $context): iterable
     {
         return [
-            'name' => $institute['Name'],
+            'name' => (string) $institute['Name'],
             'city' => $institute['Plz'],
             'street' => $institute['Strasse'],
             'phone' => $institute['telefon'],