Modifying a structure field value causes an error with no stack trace

[hdodov]

Describe the bug Manually turning a structure value from string into array causes an error with no stack trace.

To Reproduce Steps to reproduce the behavior:

1. Download the Kirby Starterkit

2. Modify content/3_about/about.txt from:

   -
     platform: Twitter

   ...to

   -
     platform:
       - Twitter

3. Open the homepage

4. You should see the following error:

   

Expected behavior A stack trace telling you where the error came from.

Kirby Version 3.1.2

Desktop (please complete the following information):

• OS: Windows 10
• Chrome
• 73.0.3683.103 (Official Build) (64-bit)

[distantnative]

For me there is a stack trace: