Null values in environent variables may cause a build to fail with a NPE

com.atlassian.bamboo.task.TaskException: Failed to execute task
at com.atlassian.bamboo.plugins.shell.task.AbstractShellBuildTask.execute(AbstractShellBuildTask.java:84)
at com.atlassian.bamboo.plugins.script.task.ScriptBuildTask.execute(ScriptBuildTask.java:53)
at com.atlassian.bamboo.task.TaskExecutorImpl.executeTasks(TaskExecutorImpl.java:180)
at com.atlassian.bamboo.task.TaskExecutorImpl.execute(TaskExecutorImpl.java:88)
at com.atlassian.bamboo.build.pipeline.tasks.ExecuteBuildTask.call(ExecuteBuildTask.java:88)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:304)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
at org.springframework.orm.hibernate.HibernateInterceptor.invoke(HibernateInterceptor.java:117)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at $Proxy465.call(Unknown Source)
at com.atlassian.bamboo.v2.build.agent.DefaultBuildAgent.build(DefaultBuildAgent.java:198)
at com.atlassian.bamboo.v2.build.agent.BuildAgentControllerImpl.waitAndPerformBuild(BuildAgentControllerImpl.java:99)
at com.atlassian.bamboo.v2.build.agent.DefaultBuildAgent$1.run(DefaultBuildAgent.java:107)
at com.atlassian.bamboo.build.pipeline.concurrent.NamedThreadFactory$2.run(NamedThreadFactory.java:50)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NullPointerException
at com.atlassian.bamboo.process.EnvironmentVariableAccessorImpl.validateEnvironmentVariables(EnvironmentVariableAccessorImpl.java:176)
at com.atlassian.bamboo.process.EnvironmentVariableAccessorImpl.validateEnvironmentVariables(EnvironmentVariableAccessorImpl.java:161)
at com.atlassian.bamboo.process.ProcessServiceImpl.createProcess(ProcessServiceImpl.java:139)
at com.atlassian.bamboo.process.ProcessServiceImpl.executeProcess(ProcessServiceImpl.java:175)
at com.atlassian.bamboo.plugins.shell.task.AbstractShellBuildTask.execute(AbstractShellBuildTask.java:62)
... 20 more