Small bug fix

Author: cffls

pycardano/backend/ogmios.py

@@ -287,7 +287,7 @@ def _get_datum_from_kupo(self, datum_hash: str) -> Optional[RawCBOR]:
         """
         datum = self._datum_cache.get(datum_hash, None)
 
-        if datum is not None or (datum is None and not self._is_chain_tip_updated()):
+        if datum is not None or (datum_hash in self._datum_cache and not self._is_chain_tip_updated()):
             return datum
 
         if self._kupo_url is None: