Fix automation chain's YAML editor when dealing with MVEL expression in 'Properties' parameters

The value of the parameter of type Properties of an operation containing a MVEL expression is lost when switching to the YAML editor.

How to reproduce:

• create a new automation chain
• add a Document.Create operation with Type parameter set to File and Properties parameter set to

  @{Context.get("docMetaData")}
  

• add a Document.Update operation with Properties parameter set to

  @{Context.get("docMetaData")}
  

• click on the Switch editor button to switch to the YAML editor

Expected result: Properties parameter of operation Document.Create and Document.Update contains

@{Context.get(\"docMetaData\")}

Actual result: Properties parameter of operation Document.Create and Document.Update contains

{}

Then switching back to the regular editor generates an error.