fix: warning on isNumber()

refs #604

src/app/util/util.ts

@@ -13,7 +13,7 @@ export function logObject(obj: {}, m?: string) {
 }
 
 export function isNumber(s: string): boolean {
-    return Number(s) !== NaN;
+    return !Number.isNaN(Number(s));
 }
 
 /**