@Nonnull
    public List<AssemblyConfiguration> getAssembliesConfiguration() {
        final List<AssemblyConfiguration> assemblyConfigurations = new ArrayList<>();

        if (assemblies != null) {
            for (AssemblyConfiguration config : assemblies) {
                if (config != null) {
                    assemblyConfigurations.add(config);
                }
            }
        }

        return assemblyConfigurations;
    }
Use {@link #getAllAssemblyConfigurations()} unless you specifically want the configuration defined only by <code>assemblies</code>.
src/main/java/io/fabric8/maven/docker/config/BuildImageConfiguration.java