don't notify cancelled trips

src/model/tripdetails.rs

@@ -77,6 +77,10 @@ WHERE day = ? AND planned_starting_time = ?
         .await.unwrap()
     }
 
+    pub fn cancelled(&self, db: &SqlitePool) -> bool {
+        self.max_people == 0
+    }
+
     /// This function is called when a person registers to a trip or when the cox changes the
     /// amount of free places.
     pub async fn check_free_spaces(&self, db: &SqlitePool) {
@@ -85,7 +89,7 @@ WHERE day = ? AND planned_starting_time = ?
             return;
         }
 
-        if self.max_people == 0 {
+        if self.cancelled(db) {
             // Cox cancelled event, thus it's probably bad weather. Don't bother with sending
             // notifications
             return;