Do not raise a 500 exception when previewing empty media. (#8883)

1 files changed, 5 insertions, 1 deletions

diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py

index dce6c4d168..1082389d9b 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -676,7 +676,11 @@ class PreviewUrlResource(DirectServeJsonResource):
             logger.debug("No media removed from url cache")
 
 
-def decode_and_calc_og(body, media_uri, request_encoding=None):
+def decode_and_calc_og(body, media_uri, request_encoding=None) -> Dict[str, str]:
+    # If there's no body, nothing useful is going to be found.
+    if not body:
+        return {}
+
     from lxml import etree
 
     try: