when an object with NULL id is given to update() method in Transport class, it fails with NPE

[alexeyOnGitHub]

it should fail with something more dev-friendly to simplify debug. RuntimeException or IllegalArgumentException or something.

this is applicable to all updateXX() calls to Redmine Java API, which use Transport class internally:

• issueManager.update(issue)
• membershipManager.update(membership)
• etc.