Fix empty string on app error (#15166)

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."