fix error when no backup

rust/src/webserver/webserver.rs

@@ -188,7 +188,14 @@ fn backup_info(
             };
             serde_json::to_string(&wbh)?
         }
-        Err(_) => "{\"error\":\"Header could not be parsed\"".to_owned(),
+        Err(_) => {
+            //TODO make better
+            let wbh = WebBackupHeader {
+                timestamp: "no backup".to_owned(),
+                size: 0,
+            };
+            serde_json::to_string(&wbh)?
+        }
     };
     anyhow::Ok(Some(json))
 }