Don't throw an error when contains stmt or comp stmt are applied on a non-existent field

[marcauberer]

For Compose Generator we have following single statement:

services.database contains name == "elasticsearch"

This is problematic, because currently CCom terminates with an error if the key services.database does not exist. Same thing for compStmts.
As we currently only support a logical or (|) and no logical and, we cannot check if the key services.database exists before executing the statement above.

A solution for that would be to simply evaluate comp and contain statements to false if the key does not even exist.