In case of exception occuring during construction
of a Sass type instance just return Undefined value,
as the delayed JS exception will pop up later.

The following code:

    var sass = require('./');
        sass.render({
        data: 'div { color: foo(); }',
          functions: {
            'foo()': function() {
              return sass.types.Color(2,3);
            }
          }
    });

now results in an libsass error

     Constructor should be invoked with either 0, 1, 3 or 4 arguments

instead of V8 abort

     FATAL ERROR: v8::ToLocalChecked Empty MaybeLocal