fix: tolerate unavailable browser timezone data

frontend/tomorrow-plan.js

@@ -27,8 +27,15 @@ function createTomorrowPlan({fetchJson,localDate,timeZone}={}) {
   function millisecondsUntilNextDay() {
     const now=Date.now();
     const zone=timeZone();
-    const formatter=new Intl.DateTimeFormat('en-CA',{timeZone:zone,year:'numeric',month:'2-digit',day:'2-digit',
-      hour:'2-digit',minute:'2-digit',second:'2-digit',hourCycle:'h23'});
+    let formatter;
+    try {
+      formatter=new Intl.DateTimeFormat('en-CA',{timeZone:zone,year:'numeric',month:'2-digit',day:'2-digit',
+        hour:'2-digit',minute:'2-digit',second:'2-digit',hourCycle:'h23'});
+    } catch (_error) {
+      const next=new Date(now);
+      next.setHours(24,0,0,250);
+      return Math.max(1,next.getTime()-now);
+    }
     const zoned=value=>Object.fromEntries(formatter.formatToParts(new Date(value))
       .filter(part=>part.type!=='literal').map(part=>[part.type,Number(part.value)]));
     const current=zoned(now);