getting null point exception in mvn install

[INFO] Scanning for projects...
[ERROR] Internal error: java.lang.NullPointerException -> [Help 1]
org.apache.maven.InternalErrorException: Internal error: java.lang.NullPointerException
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:120)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:957)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:289)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:193)
    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:282)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)
Caused by: java.lang.NullPointerException
    at java.util.Hashtable$Entry.setValue (Hashtable.java:1286)
    at org.apache.maven.model.interpolation.StringVisitorModelInterpolator$ModelVisitor.visit (StringVisitorModelInterpolator.java:1429)
    at org.apache.maven.model.interpolation.StringVisitorModelInterpolator$ModelVisitor.visit (StringVisitorModelInterpolator.java:1027)
    at org.apache.maven.model.interpolation.StringVisitorModelInterpolator$ModelVisitor.visit (StringVisitorModelInterpolator.java:170)
    at org.apache.maven.model.interpolation.StringVisitorModelInterpolator.interpolateModel (StringVisitorModelInterpolator.java:107)
    at org.apache.maven.model.building.DefaultModelBuilder.interpolateModel (DefaultModelBuilder.java:789)
    at org.apache.maven.model.building.DefaultModelBuilder.build (DefaultModelBuilder.java:393)
    at org.apache.maven.project.DefaultProjectBuilder.build (DefaultProjectBuilder.java:448)
    at org.apache.maven.project.DefaultProjectBuilder.build (DefaultProjectBuilder.java:414)
    at org.apache.maven.project.DefaultProjectBuilder.build (DefaultProjectBuilder.java:377)
    at org.apache.maven.graph.DefaultGraphBuilder.collectProjects (DefaultGraphBuilder.java:414)
    at org.apache.maven.graph.DefaultGraphBuilder.getProjectsForMavenReactor (DefaultGraphBuilder.java:405)
    at org.apache.maven.graph.DefaultGraphBuilder.build (DefaultGraphBuilder.java:82)
    at org.apache.maven.DefaultMaven.buildGraph (DefaultMaven.java:507)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:219)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:957)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:289)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:193)
    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:282)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/InternalErrorException