Improve validation

Author: timmo001

src/panels/lovelace/common/validate-condition.ts

@@ -293,10 +293,14 @@ function validateScreenCondition(condition: ScreenCondition) {
 }
 
 function validateTimeCondition(condition: TimeCondition) {
-  return (
-    (condition.after != null || condition.before != null) &&
-    condition.weekdays?.every((w: WeekdayShort) => WEEKDAYS_SHORT.includes(w))
-  );
+  const hasTime = condition.after != null || condition.before != null;
+  const hasWeekdays =
+    condition.weekdays != null && condition.weekdays.length > 0;
+  const weekdaysValid =
+    !hasWeekdays ||
+    condition.weekdays!.every((w: WeekdayShort) => WEEKDAYS_SHORT.includes(w));
+
+  return (hasTime || hasWeekdays) && weekdaysValid;
 }
 
 function validateUserCondition(condition: UserCondition) {