Bugfix in LDLf test parser

[cipollone]

Proposed changes

The parser object for the LDLf Test operator was read incorrectly. We were reading the token ? instead of the associated formula.
Waning: I debugged through logaut. I didn't execute this repo directly.

Types of changes

What types of changes does your code introduce?
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

[marcofavorito]

LGTM