One option to try is to use the ago-assistant to edit the application data associated with that appid. Note that if you can reproduce this with a test app you may want to try these steps there first to avoid breaking your production app.
You can log-in to the ago-assistant app using the link below and use it to update urls, copy content, edit json associated with an item and more. But as I mentioned earlier it is possible to break your data doing this so try working off a backup first.
https://ago-assistant.esri.com/
After logging in choose 'View an item's JSON' from the I want to dropdown list. Then find the name of the app item you want to edit and click it and you'll see that the json for your app is displayed. This is displayed in two parts the item description and the data. The part you'll want to edit for the app is the 'Data' so scroll down to find that section. Here's an example of what it looks like on my end.
Use the pencil icon to edit the data and replace the searchConfig portion of the json with the following:
"searchConfig": {
"sources": [],
"activeSourceIndex": 0,
"enableSearchingAll": false
},After making the above edit - and before hitting save - it would be a good idea to copy all the content from the Data section and check that its still valid json using a tool like jsonlint.com.
So I thought the issue had been fixed. After creating a simple map as a test this morning all was working great with changing the configuration and saving without issues. I then went to recreate my original utility look up map app form scratch. All worked good and I was able to use configure app and then save or save & view without any issues. I left the app for a bit and when I came back it allowed me to go into configure app and make a few changes and save, working as expected. However within a short time when I click save or save & view I started to get the loading gif icon that goes on for ever. It only stops when I click close button. So I was back to the same issue as I was having on my original map app.
In debugger I am getting the same error code in the same location "TypeError p is null and it references Configure. :112:1 like it was earlier today and previously.
So it seemed to be fixed, but after using the configure app function it goes back to its old behaviors of locking on save.
Anymore info from Tech Support on a viable solution for getting it to work properly? It is an awesome template and I have other ideas on how to use it for other projects, but if is keeps locking up on save it really cannot be used. 
