guarda against firefox lack of weekInfo

Author: jaimergp

src/components/Calendar/index.jsx

@@ -1,20 +1,21 @@
 import { React, useEffect, useState } from "react";
 
-
 export default function Calendar() {
   const [state, setState] = useState({
     firstDay: 1,
-    timezone: 'UTC',
+    timezone: "UTC",
   });
-  useEffect(() => {
-    const locale = Intl.DateTimeFormat().resolvedOptions().locale;
-    const firstDay = (new Intl.Locale(locale)).weekInfo.firstDay + 1;
-    const timezone = Intl.DateTimeFormat().resolvedOptions().timeZone;
-    setState({firstDay: firstDay, timezone: timezone});
-  })
+  if (Intl) {
+    useEffect(() => {
+      const locale = Intl.DateTimeFormat().resolvedOptions().locale;
+      const firstDay = (new Intl.Locale(locale)?.weekInfo?.firstDay ?? 0) + 1;
+      const timezone = Intl.DateTimeFormat().resolvedOptions().timeZone;
+      setState({ firstDay: firstDay, timezone: timezone });
+    });
+  }
   return (
     <iframe
-      src={ `https://calendar.google.com/calendar/embed?height=500&wkst=${state.firstDay}&ctz=${state.timezone}&showTitle=0&showTz=1&showPrint=0&src=ODgwNTU3MGE0ZTFjYTIzMTk4NDI5NzFkYjQzODBlZDUxOGM0OTA1NzdjMDY0NTRhZGYyMzAzNzM0NTA2ZjM5N0Bncm91cC5jYWxlbmRhci5nb29nbGUuY29t&color=%2333b679` }
+      src={`https://calendar.google.com/calendar/embed?height=500&wkst=${state.firstDay}&ctz=${state.timezone}&showTitle=0&showTz=1&showPrint=0&src=ODgwNTU3MGE0ZTFjYTIzMTk4NDI5NzFkYjQzODBlZDUxOGM0OTA1NzdjMDY0NTRhZGYyMzAzNzM0NTA2ZjM5N0Bncm91cC5jYWxlbmRhci5nb29nbGUuY29t&color=%2333b679`}
       width="100%"
       height="500"
       frameborder="0"