setting gemJars does not work as expected

[fcarter]

Assumption: setting gemJars in the compass configuration should use the provided jar(s) to obtain the Ruby gems rather that fetching over the network. This is important in some environments due to network
access & proxy topology issues.

In 1.0.10, setting gemJars has no apparent affect.

Looking into things, in DependenciesResolver.groovy, the check is made for "if (gemJars?.empty)..". I believe that "empty" is not a valid property here, but due to groovy's forgiving nature, the test is allowed (I suspect it's treating things like a map & looking for a key named empty).

I made a local fix by changing the test to "if (gemJars?.isEmpty())...", wherein things seemed to work as (I) expected.

I would upload the fix, but running the tests seems to generate a number of (seemingly unrelated) MIssingMethodExceptions (ImageGenerationSpec.groovy:24, :37, :50, :63 -- apparently about project.runTasks). I may be using an older groovy, gradle, or something. At any rate, without getting a successful build, I'm hesitant to push a change.