`adjustBallast` function fails

[gbarter]

Description

When I give RAFT the trim_ballast option and have it set to adjustBallast with this function, there is an error on this line because the "headings" property is never created for Member objects.

Steps to reproduce issue

Please provide a minimum working example (MWE) if possible
Use this example, but instead call model.analyzeUnloaded(ballast=1)

Current behavior

12:43:18 gbarter-37067s ~/devel/RAFT/examples $python example_from_yaml.py 
Making FOWT
Mesh characteristic lengths: min=1.0, max=3.0
adjusting ballast fill levels
Traceback (most recent call last):
  File "/Users/gbarter/devel/RAFT/examples/example_from_yaml.py", line 43, in <module>
    run_example(plot_flag = plot_flag)
  File "/Users/gbarter/devel/RAFT/examples/example_from_yaml.py", line 17, in run_example
    model.analyzeUnloaded(ballast=1)
  File "/Users/gbarter/devel/RAFT/raft/raft_model.py", line 229, in analyzeUnloaded
    self.adjustBallast(fowt, heave_tol=heave_tol)  
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/gbarter/devel/RAFT/raft/raft_model.py", line 1462, in adjustBallast
    if np.isscalar(member.headings):
                   ^^^^^^^^^^^^^^^
AttributeError: 'Member' object has no attribute 'headings'

Code versions

Both master and dev branches have the bug

[gbarter]

A good opportunity to add a unit test or regression test!

[lucas-carmo]

Thanks, @gbarter! I'll take a look at that as soon as possible