Parse push ping parameter with parseInt.

server/routers/api-router.js

@@ -37,7 +37,7 @@ router.get("/api/push/:pushToken", async (request, response) => {
 
         let pushToken = request.params.pushToken;
         let msg = request.query.msg || "OK";
-        let ping = request.query.ping || null;
+        let ping = parseInt(request.query.ping) || null;
         let statusString = request.query.status || "up";
         let status = (statusString === "up") ? UP : DOWN;