av-store: create a db dir if missing (#1819)

polkadot/node/core/av-store/src/lib.rs

@@ -106,6 +106,7 @@ impl AvailabilityStoreSubsystem {
 			format!("Bad database path: {:?}", config.path),
 		))?;
 
+		std::fs::create_dir_all(&path)?;
 		let db = Database::open(&db_config, &path)?;
 
 		Ok(Self {