Can't access Activator/BundleContext during shared service initialization

Steps to reproduce:

1. create a service (Java class) that accesses something like Activator.getDefault().getBundle().getBundleContext().getServiceReference(SomeService.class) in the constructor.
2. bind the service in a custom shared state module that has been registered via Xtext's extension point.
3. Starting org.eclipse.xtext.ui.shared will now fail.

Analysis: the code from (1) throws an NPE because it's called during org.eclipse.xtext.ui.shared.internal.Activator.start(BundleContext)

Since the bundle can't be activated users see tons of subsequent ClassNotFoundExceptions because classes from that bundle can't be accessed.

While I don't think the code from (1) needs to be supported in any case... I can say that this used to work because the Shared Injector used to be initialized lazily and thus after bundle startup finished.

Start with org.eclipse.xtext.ui.shared.internal.Activator.start(BundleContext) and trace how the custom shared state module is initialized through Xtext's extension point. Reproduce the constructor access to Activator.getDefault().getBundle().getBundleContext() and determine the initialization ordering that causes the NPE. Done means org.eclipse.xtext.ui.shared starts successfully without the subsequent ClassNotFoundExceptions.