Fix multiline values when switching editors in Automation Chain editor

1. Create an automation chain.
2. Add Document.Create to your chain.
3. Set any value for type (@{Document.id} for example).
4. Set the following value for properties:

key=multiline\
value

When switching to the code editor and back to the visual one, you would expect this value to remain the same, but you'll see that the value for properties has been changed to:

key=multilinvalue

(discovered by Bertrand while testing the fix for NXS-4803)