getting Null pointer exception

[aruruvishal49]

WARN [main] - unresolved dependency: org.walkmod#walkmod-imports-cleaner-plugin;latest.integration: not found
WARN [main] - unresolved dependency: org.walkmod#walkmod-maven-plugin;latest.integration: not found
WARN [main] - unresolved dependency: org.walkmod#walkmod-javalang-plugin;[2.0, 4.0): not found
ERROR [main] - Invalid configuration
org.walkmod.conf.ConfigurationException: Ivy can not resolve the artifacts. Cause: unresolved dependency: org.walkmod#walkmod-imports-cleaner-plugin;latest.integration: not found;unresolved dependency: org.walkmod#walkmod-maven-plugin;latest.integration: not found;unresolved dependency: org.walkmod#walkmod-javalang-plugin;[2.0, 4.0): not found
at org.walkmod.conf.providers.IvyConfigurationProvider.resolveArtifacts(IvyConfigurationProvider.java:233)
at org.walkmod.conf.providers.IvyConfigurationProvider.load(IvyConfigurationProvider.java:156)
at org.walkmod.conf.ConfigurationManager.executeConfigurationProviders(ConfigurationManager.java:124)
at org.walkmod.conf.ConfigurationManager.addProviders(ConfigurationManager.java:61)
at org.walkmod.conf.ConfigurationManager.(ConfigurationManager.java:75)
at org.walkmod.conf.ConfigurationManager.(ConfigurationManager.java:79)
at org.walkmod.WalkModFacade.readConfig(WalkModFacade.java:181)
at org.walkmod.WalkModFacade.run(WalkModFacade.java:256)
at org.walkmod.WalkModFacade.apply(WalkModFacade.java:142)
at org.walkmod.commands.ApplyCommand.execute(ApplyCommand.java:40)
at org.walkmod.WalkModDispatcher.execute(WalkModDispatcher.java:172)
at org.walkmod.WalkModDispatcher.main(WalkModDispatcher.java:197)
ERROR [main] - Invalid configuration
java.lang.NullPointerException
at org.walkmod.WalkModFacade.run(WalkModFacade.java:264)
at org.walkmod.WalkModFacade.apply(WalkModFacade.java:142)
at org.walkmod.commands.ApplyCommand.execute(ApplyCommand.java:40)
at org.walkmod.WalkModDispatcher.execute(WalkModDispatcher.java:172)
at org.walkmod.WalkModDispatcher.main(WalkModDispatcher.java:197)
Exception in thread "main" java.lang.NullPointerException
at org.walkmod.WalkModFacade.run(WalkModFacade.java:284)
at org.walkmod.WalkModFacade.apply(WalkModFacade.java:142)
at org.walkmod.commands.ApplyCommand.execute(ApplyCommand.java:40)
at org.walkmod.WalkModDispatcher.execute(WalkModDispatcher.java:172)
at org.walkmod.WalkModDispatcher.main(WalkModDispatcher.java:197)

My walkmod.xml

<!DOCTYPE walkmod PUBLIC "-//WALKMOD//DTD" "http://www.walkmod.com/dtd/walkmod-1.1.dtd">
<walkmod>
    <transformation type="imports-cleaner"/>
</walkmod>

I am running the command : walkmod apply

[Astro03]

I'm getting a similar error.

ERROR [main] - Invalid configuration
java.lang.NullPointerException: Cannot invoke "org.walkmod.conf.entities.Configuration.executeModuleChains(org.walkmod.Options, org.walkmod.WalkmodCommand, String[])" because "config" is null
	at org.walkmod.WalkModFacade.run(WalkModFacade.java:264)
	at org.walkmod.WalkModFacade.apply(WalkModFacade.java:142)
	at org.walkmod.commands.ApplyCommand.execute(ApplyCommand.java:40)
	at org.walkmod.WalkModDispatcher.execute(WalkModDispatcher.java:172)
	at org.walkmod.WalkModDispatcher.main(WalkModDispatcher.java:197)
Exception in thread "main" java.lang.NullPointerException: Cannot invoke "org.walkmod.conf.entities.Configuration.execute(String, org.walkmod.Options, String[])" because "config" is null
	at org.walkmod.WalkModFacade.run(WalkModFacade.java:284)
	at org.walkmod.WalkModFacade.apply(WalkModFacade.java:142)
	at org.walkmod.commands.ApplyCommand.execute(ApplyCommand.java:40)
	at org.walkmod.WalkModDispatcher.execute(WalkModDispatcher.java:172)
	at org.walkmod.WalkModDispatcher.main(WalkModDispatcher.java:197)

For me, I believe it's caused by not being able to resolve an artifact: org.gradle#gradle-tooling-api;2.10

org.walkmod.conf.ConfigurationException: Ivy can not resolve the artifacts. Cause: unresolved dependency: org.gradle#gradle-tooling-api;2.10: not found