feat: Separate in method: _syncLabelForOpenedEmail & add const for LabelKeywordIsNull

lib/features/labels/presentation/mixin/add_label_to_email_mixin.dart

@@ -87,7 +87,7 @@ mixin AddLabelToEmailMixin on EmitStateMixin {
       emitFailure(
         controller: currentController,
         failure: AddALabelToAnEmailFailure(
-          exception: LabelKeywordIsNull(),
+          exception: const LabelKeywordIsNull(),
           labelDisplay: labelDisplay,
         ),
       );
@@ -151,7 +151,7 @@ mixin AddLabelToEmailMixin on EmitStateMixin {
       emitFailure(
         controller: currentController,
         failure: RemoveALabelFromAnEmailFailure(
-          exception: LabelKeywordIsNull(),
+          exception: const LabelKeywordIsNull(),
           labelDisplay: labelDisplay,
         ),
       );

lib/features/mailbox_dashboard/presentation/extensions/labels/handle_logic_label_extension.dart

@@ -49,6 +49,15 @@ extension HandleLogicLabelExtension on MailboxDashBoardController  {
     _refreshLabelSettingEnabled();
 
     if (isEmailOpened) {
+      _syncLabelForOpenedEmail(emailId, labelKeyword, shouldRemove);
+    }
+  }
+
+  void _syncLabelForOpenedEmail(
+    EmailId emailId,
+    KeyWordIdentifier labelKeyword,
+    bool shouldRemove,
+  ) {
     dispatchEmailUIAction(
       SyncUpdateLabelForEmailOnMemory(
         emailId: emailId,
@@ -57,7 +66,6 @@ extension HandleLogicLabelExtension on MailboxDashBoardController  {
       ),
     );
   }
-  }
 
   void _syncLabelForEmailList(
     EmailId emailId,