Fix empty string on app error (#15166)

app/user.go

@@ -2172,7 +2172,7 @@ func (a *App) ConvertBotToUser(bot *model.Bot, userPatch *model.UserPatch, sysad
 
 	appErr := a.Srv().Store.Bot().PermanentDelete(bot.UserId)
 	if appErr != nil {
-		return nil, model.NewAppError("ConvertBotToUser", "", nil, err.Error(), http.StatusInternalServerError)
+		return nil, model.NewAppError("ConvertBotToUser", "app.user.convert_bot_to_user.app_error", nil, err.Error(), http.StatusInternalServerError)
 	}
 
 	return user, nil

i18n/en.json

@@ -1,8 +1,4 @@
 [
-  {
-    "id": "",
-    "translation": ""
-  },
   {
     "id": "April",
     "translation": "April"
@@ -4434,6 +4430,10 @@
     "id": "app.user.complete_switch_with_oauth.blank_email.app_error",
     "translation": "Unable to complete SAML login with an empty email address."
   },
+  {
+    "id": "app.user.convert_bot_to_user.app_error",
+    "translation": "Unable to convert bot to user."
+  },
   {
     "id": "app.user.permanentdeleteuser.internal_error",
     "translation": "Unable to delete user."