Don't pretty-print unparseable test suite types.

Issue #1202. The pretty printer was printing 'type: -' for empty test
suite interfaces.  The empty test interface type is the result of
parsing a branch in a conditional block where no type is explicitly
specified (i.e., the type is inherited from a higher level or propagated
up from a lower one).  Therefore, the pretty-printer should not print
any 'type' field at all for test suites with an empty test interface
type.