handle avatar delete error while avatar is in use

Handler/Avatar.hs

@@ -118,9 +118,15 @@ getAvatarDeleteR aId = do
   ma <- runDB $ get aId
   case ma of
     Just _ -> do
-      runDB $ delete aId
-      setMessageI MsgAvatarDeleted
-      redirect $ HomeR
+      c <- runDB $ selectList [UserAvatar ==. Just aId] []
+      case null c of
+        True -> do
+          runDB $ delete aId
+          setMessageI MsgAvatarDeleted
+          redirect $ HomeR
+        False -> do
+          setMessageI MsgAvatarInUseError
+          redirect $ AvatarR
     Nothing -> do
       setMessageI MsgAvatarUnknown
       redirect $ AvatarR

messages/cz.msg

@@ -96,3 +96,4 @@ NewAvatar: Nový avatar
 AvatarUploadSuccessfull: Avatar úspěšně nahrán
 DeleteAvatar: Smazat avatar
 AvatarDeleted: Avatar úspěšně smazán
+AvatarInUseError: Avatar nelze smazat dokud je v užitku

messages/de.msg

@@ -96,3 +96,4 @@ NewAvatar: Neuer Avatar
 AvatarUploadSuccessfull: Avatar erfolgreich hochgeladen
 DeleteAvatar: Diesen Avatar löschen
 AvatarDeleted: Avatar gelöscht
+AvatarInUseError: Avatare können nicht gelöscht werden, solange sie in Benutzung sind.

messages/en.msg

@@ -96,3 +96,4 @@ NewAvatar: New avatar
 AvatarUploadSuccessfull: Avatar upload successfull
 DeleteAvatar: Delete avatar
 AvatarDeleted: Avatar successfully deleted
+AvatarInUseError: You can not delete avatars that are currently in use