Augmenting a choice without a case from another module causes NPE

I tried to add the following grouping to odl-lisp-proto.yang (https://git.opendaylight.org/gerrit/gitweb?p=lispflowmapping.git;a=blob;f=mappingservice/lisp-proto/src/main/yang/odl-lisp-proto.yang;h=58bf372611c9937ec6c9a373966a3c8275f548a4;hb=HEAD):

grouping augmented-lisp-address {
uses lisp-address:lisp-address {
augment "address" {
leaf ipv4-binary

{ type bin:ipv4-address-binary; description "IPv4 (binary) address."; }

}
}
}

I'm not saying that what I'm trying to do is correct, but I recall Robert saying that a NPE is generally a bug, so here's the resulting trace, when building:

[INFO] yang-to-sources: Sources will be generated to /Users/lojakab/src/opendaylight/lispflowmapping/mappingservice/lisp-proto/target/generated-sources/mdsal-binding
[ERROR] yang-to-sources: Unable to generate sources with org.opendaylight.yangtools.maven.sal.api.gen.plugin.CodeGeneratorImpl generator
java.lang.NullPointerException
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.generateTypesFromAugmentedChoiceCases(BindingGeneratorImpl.java:1333)
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.usesAugmentationToGenTypes(BindingGeneratorImpl.java:873)
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.processUsesAugments(BindingGeneratorImpl.java:377)
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.groupingToGenType(BindingGeneratorImpl.java:709)
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.groupingsToGenTypes(BindingGeneratorImpl.java:684)
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.moduleToGenTypes(BindingGeneratorImpl.java:262)
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.generateTypes(BindingGeneratorImpl.java:240)
at org.opendaylight.yangtools.maven.sal.api.gen.plugin.CodeGeneratorImpl.generateSources(CodeGeneratorImpl.java:61)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.generateSourcesWithOneGenerator(YangToSourcesProcessor.java:340)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.generateSources(YangToSourcesProcessor.java:285)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.execute(YangToSourcesProcessor.java:95)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesMojo.execute(YangToSourcesMojo.java:116)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
[ERROR] yang-to-sources: One or more code generators failed, including failed list(generatorClass=exception)

{org.opendaylight.yangtools.maven.sal.api.gen.plugin.CodeGeneratorImpl=java.lang.NullPointerException}