LEAF ENUM TYPE issue: DUPLICATE enum name cauisng null pointer exception. Its should throw error related to duplication

leaf ifType {
type enumeration {
enum "unbounded";
enum ZERO;
enum two;
enum four;
enum seven

{ value 2147483647; }

enum seven

{ value 1234; }

}
}

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[INFO] Building onlab-rest 1.6.0-SNAPSHOT
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[INFO] — maven-clean-plugin:2.5:clean (default-clean) @ onlab-rest —
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[INFO] — jacoco-maven-plugin:0.7.5.201505241946:prepare-agent (default-prepare-agent) @ onlab-rest —
[INFO] argLine set to -javaagent:/root/.m2/repository/org/jacoco/org.jacoco.agent/0.7.5.201505241946/org.jacoco.agent-0.7.5.201505241946-runtime.jar=destfile=/home/root1/onos/utils/test/target/jacoco.exec -Duser.language=en -Duser.region=US
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[INFO] — yangutils-maven-plugin:1.0.0-SNAPSHOT:yang2java (default) @ onlab-rest —
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java.lang.NullPointerException
at org.onosproject.yangutils.parser.impl.listeners.EnumListener.processEnumExit(EnumListener.java:164)
at org.onosproject.yangutils.parser.impl.TreeWalkListener.exitEnumStatement(TreeWalkListener.java:636)
at org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser$EnumStatementContext.exitRule(GeneratedYangParser.java:8506)
at org.antlr.v4.runtime.tree.ParseTreeWalker.exitRule(ParseTreeWalker.java:71)
at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:54)
at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:52)
at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:52)
at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:52)
at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:52)
at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:52)
at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:52)
at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:52)
at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:52)
at org.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:52)
at org.onosproject.yangutils.parser.impl.YangUtilsParserManager.getDataModel(YangUtilsParserManager.java:92)
at org.onosproject.yangutils.plugin.manager.YangUtilManager.execute(YangUtilManager.java:148)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
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:862)
at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:286)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:197)
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)
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[INFO] BUILD FAILURE
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