caught an NPE when calling the GithubProjectProperty.projectUrl, returned null in the catch in keeping with the if(tcc.projectUrl == null) check
adding a logging message if the projectUrl cannot be found in the existing config
removing the try/catch and replacing with separate checks for JSON binding and the existence of the project URL
[FIXED JENKINS-20201]

I'm actually unclear why bindJSON can return null at all.
But I'm not going to let that mystery block users.
Merge pull request #34