fix in get_preview_file

Author: bcrickboom

orthanc_api_client/resources/series_list.py

@@ -57,7 +57,7 @@ def get_preview_file(self, orthanc_id: str, jpeg_format: bool = False, return_un
             headers = { "Accept": "image/png"}
 
         if return_unsupported_image:
-            parameters = {"returnUnsupportedImage": True}
+            parameters = {"returnUnsupportedImage": "true"}
         else:
             parameters = {}
         return self._api_client.get_binary(endpoint=url, headers=headers, params=parameters, allow_redirects=True)