while trying to check JBIDE-18559 I clicked "checked for updates" in central and got nothing, not even a dialog.

In error log it was reporting this:

org.eclipse.equinox.p2.core.ProvisionException: No repository found at file:/Users/max/code/jbdevstudio/linuxtools-docker/org.eclipse.linuxtools.docker.core/target/.
at org.eclipse.equinox.internal.p2.repository.helpers.AbstractRepositoryManager.fail(AbstractRepositoryManager.java:395)
at sun.reflect.GeneratedMethodAccessor97.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at org.eclipse.oomph.util.ReflectUtil.invokeMethod(ReflectUtil.java:116)
at org.eclipse.oomph.p2.internal.core.CachingRepositoryManager.fail(CachingRepositoryManager.java:284)
at org.eclipse.oomph.p2.internal.core.CachingRepositoryManager.loadRepository(CachingRepositoryManager.java:191)
at org.eclipse.oomph.p2.internal.core.CachingRepositoryManager$Metadata.loadRepository(CachingRepositoryManager.java:378)
at org.eclipse.equinox.internal.p2.metadata.repository.MetadataRepositoryManager.loadRepository(MetadataRepositoryManager.java:96)
at org.eclipse.equinox.internal.p2.metadata.repository.MetadataRepositoryManager.loadRepository(MetadataRepositoryManager.java:92)
at org.eclipse.equinox.p2.ui.LoadMetadataRepositoryJob.doLoad(LoadMetadataRepositoryJob.java:117)
at org.eclipse.equinox.p2.ui.LoadMetadataRepositoryJob.runModal(LoadMetadataRepositoryJob.java:102)
at org.eclipse.equinox.internal.p2.ui.sdk.PreloadingRepositoryHandler$2.runModal(PreloadingRepositoryHandler.java:83)
at org.eclipse.equinox.p2.operations.ProvisioningJob.run(ProvisioningJob.java:177)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

would have expected we told the user about this error.