server: fix issue where no video files could be uploaded

server/szurubooru/func/image_hash.py

@@ -44,7 +44,7 @@ def _preprocess_image(content: bytes) -> NpMatrix:
     try:
         img = Image.open(BytesIO(content))
         return np.asarray(img.convert("L"), dtype=np.uint8)
-    except IOError:
+    except (IOError, ValueError):
         raise errors.ProcessingError(
             "Unable to generate a signature hash " "for this image."
         )