Crash when using scan on an empty plot

[Amp63]

Describe the bug If you try to use the scan feature from the API on a plot with no templates, the game crashes.

To Reproduce

1. Go to an empty plot on DF
2. Run the 'scan' command through the api, I used the following script:

   import websocket
   ws = websocket.WebSocket()
   ws.connect('ws://localhost:31375')
   ws.recv()  # auth
   ws.send('scan')
   ws.recv()  # received templates (should be nothing)
   ws.close()

Expected behavior The response is an empty string or some other indicator that no templates were found.

Screenshots Here's the crash report: https://bytebin.lucko.me/bH1lOkgVdQ

Checks Please check all these for more infomation with the bug.

• [x] I am using the latest version.
• [x] I have tried disabling various options to see if they cause the issue, such as new ones or ones I have recently enabled.

[GeorgeRNG]

A little late to commit this fix, it should now just respond with empty. (fixed in this commit)