GenericContainer::isRunning throws exception if container not started

[kprokopchik]

GenericContainer::isRunning throws exception if container not started.
This caused by null value in GenericContainer::containerId.
Expected: call GenericContainer::isRunning returns false if container not started.

[bsideup]

Hi @dhargo,

Thanks for reporting, it's an annoying bug we should finally fix. It's a trivial change to catch() block, let me know if you want to submit a PR for that 👍