Unregister the messenger everywhere on unload/navigate from

WinAppCommon/ViewModels/NewVm.cs

@@ -72,5 +72,11 @@ namespace ModernKeePass.ViewModels
             var database = await _mediator.Send(new GetDatabaseQuery());
             _navigation.NavigateTo(Constants.Navigation.GroupPage, new NavigationItem { Id = database.RootGroupId });
         }
+
+        public override void Cleanup()
+        {
+            MessengerInstance.Unregister(this);
+            base.Cleanup();
+        }
     }
 }

WinAppCommon/ViewModels/RecentVm.cs

@@ -49,5 +49,10 @@ namespace ModernKeePass.ViewModels
             _recent.ClearAll();
             RecentItems.Clear();
         }
+        public override void Cleanup()
+        {
+            MessengerInstance.Unregister(this);
+            base.Cleanup();
+        }
     }
 }

WinAppCommon/ViewModels/SaveVm.cs

@@ -69,5 +69,11 @@ namespace ModernKeePass.ViewModels
             await _mediator.Send(new CloseDatabaseCommand());
             _navigation.NavigateTo(Constants.Navigation.MainPage);
         }
+
+        public override void Cleanup()
+        {
+            MessengerInstance.Unregister(this);
+            base.Cleanup();
+        }
     }
 }

WinAppCommon/ViewModels/Settings/CredentialsVm.cs

@@ -33,5 +33,11 @@ namespace ModernKeePass.ViewModels.Settings
             var database = await _mediator.Send(new GetDatabaseQuery());
             _notification.Show(database.Name, _resource.GetResourceValue("CompositeKeyUpdated"));
         }
+
+        public override void Cleanup()
+        {
+            MessengerInstance.Unregister(this);
+            base.Cleanup();
+        }
     }
 }

WinAppCommon/ViewModels/UserControls/OpenDatabaseControlVm.cs

@@ -181,5 +181,11 @@ namespace ModernKeePass.ViewModels
                 IsOpening = false;
             }
         }
+
+        public override void Cleanup()
+        {
+            MessengerInstance.Unregister(this);
+            base.Cleanup();
+        }
     }
 }

WinAppCommon/ViewModels/UserControls/SetCredentialsVm.cs

@@ -150,5 +150,11 @@ namespace ModernKeePass.ViewModels
                 KeyFilePath = HasKeyFile ? KeyFilePath : null
             });
         }
+
+        public override void Cleanup()
+        {
+            MessengerInstance.Unregister(this);
+            base.Cleanup();
+        }
     }
 }