Introduce MaybeError type

src/core/deck.rs

@@ -6,7 +6,7 @@ use crate::core::srs::{
 use crate::data::entities::*;
 use crate::data_provider::card_stats::{load_stats_of_deck, update_stat_score};
 use crate::data_provider::history::push_note;
-use crate::notification::NotificationData;
+use crate::notification::{MaybeError, NotificationData};
 use chrono::Utc;
 use parking_lot::Mutex;
 use std::sync::Arc;
@@ -88,7 +88,7 @@ impl DeckData {
         self.current_word_index = Some(index);
         (self.words[index].clone(), self.set[index].clone())
     }
-    pub fn open(&mut self, status: WordOpenMode) -> Result<(), NotificationData> {
+    pub fn open(&mut self, status: WordOpenMode) -> MaybeError {
         if let Some(index) = self.current_word_index {
             let word: &mut CardStatistics = &mut self.set[index];
             let old_score = word.score;