Fixed DbSession.get_file_by_blob_hashes limit handling

affected compress method / hash method migration

prime_backup/db/session.py

@@ -237,7 +237,7 @@ def get_file_by_blob_hashes(self, hashes: List[str], *, limit: Optional[int] = N
 			if limit is not None:
 				st = st.limit(max(0, limit - len(result)))
 			result.extend(self.session.execute(st).scalars().all())
-			if len(result) >= limit:
+			if limit is not None and len(result) >= limit:
 				break
 		return result