Handle deleted or closed branches better

java.lang.RuntimeException: com.atlassian.bamboo.repository.RepositoryException: Cannot determine head revision of 'git@bitbucket.org:atlassian/confluence.git' on branch '4.1-stable'.
	at com.atlassian.bamboo.executor.RetryingTaskExecutor.rerun(RetryingTaskExecutor.java:119)
	at com.atlassian.bamboo.executor.RetryingTaskExecutor.runTask(RetryingTaskExecutor.java:79)
	at com.atlassian.bamboo.executor.RetryingTaskExecutor.retry(RetryingTaskExecutor.java:174)
	at com.atlassian.bamboo.v2.trigger.DefaultChangeDetectionManager.collectionChangesWithRetry(DefaultChangeDetectionManager.java:382)
	at com.atlassian.bamboo.v2.trigger.DefaultChangeDetectionManager.collectChangesSinceLastBuild(DefaultChangeDetectionManager.java:255)
	at com.atlassian.bamboo.v2.trigger.DefaultChangeDetectionManager.collectChangesSinceRevisions(DefaultChangeDetectionManager.java:213)
	at com.atlassian.bamboo.v2.trigger.DefaultChangeDetectionManager.collectChangesSinceRevisions(DefaultChangeDetectionManager.java:138)
	at com.atlassian.bamboo.v2.trigger.DefaultChangeDetectionManager.collectChangesSinceLastBuildIfTriggered(DefaultChangeDetectionManager.java:117)
	at com.atlassian.bamboo.v2.trigger.ChangeDetectionListenerAction.process(ChangeDetectionListenerAction.java:95)
	at com.atlassian.bamboo.chains.ChainExecutionManagerImpl.createChainState(ChainExecutionManagerImpl.java:245)
	at com.atlassian.bamboo.chains.ChainExecutionManagerImpl.start(ChainExecutionManagerImpl.java:168)
	at sun.reflect.GeneratedMethodAccessor343.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	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.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:89)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
	at $Proxy83.start(Unknown Source)
	at sun.reflect.GeneratedMethodAccessor343.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:304)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:198)
	at $Proxy84.start(Unknown Source)
	at com.atlassian.bamboo.plan.PlanExecutionManagerImpl.startWithLockTaken(PlanExecutionManagerImpl.java:249)
	at com.atlassian.bamboo.plan.PlanExecutionManagerImpl.access$100(PlanExecutionManagerImpl.java:40)
	at com.atlassian.bamboo.plan.PlanExecutionManagerImpl$1.call(PlanExecutionManagerImpl.java:236)
	at com.atlassian.bamboo.plan.PlanExecutionManagerImpl$1.call(PlanExecutionManagerImpl.java:230)
	at com.atlassian.util.concurrent.ManagedLocks$ManagedLockImpl.withLock(ManagedLocks.java:324)
	at com.atlassian.bamboo.plan.PlanExecutionLockServiceImpl.lock(PlanExecutionLockServiceImpl.java:68)
	at com.atlassian.bamboo.plan.PlanExecutionManagerImpl.doWithProcessLock(PlanExecutionManagerImpl.java:360)
	at com.atlassian.bamboo.plan.PlanExecutionManagerImpl.start(PlanExecutionManagerImpl.java:229)
	at com.atlassian.bamboo.plan.NonBlockingPlanExecutionServiceImpl$1.call(NonBlockingPlanExecutionServiceImpl.java:70)
	at com.atlassian.bamboo.plan.NonBlockingPlanExecutionServiceImpl$1.call(NonBlockingPlanExecutionServiceImpl.java:61)
	at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
	at java.util.concurrent.FutureTask.run(FutureTask.java:138)
	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
	at com.atlassian.bamboo.build.pipeline.concurrent.NamedThreadFactory$2.run(NamedThreadFactory.java:50)
	at java.lang.Thread.run(Thread.java:680)
Caused by: com.atlassian.bamboo.repository.RepositoryException: Cannot determine head revision of 'git@bitbucket.org:atlassian/confluence.git' on branch '4.1-stable'.
	at com.atlassian.bamboo.plugins.git.GitOperationHelper$3.doWithFetchConnection(GitOperationHelper.java:302)
	at com.atlassian.bamboo.plugins.git.GitOperationHelper$3.doWithFetchConnection(GitOperationHelper.java:295)
	at com.atlassian.bamboo.plugins.git.GitOperationHelper.withFetchConnection(GitOperationHelper.java:693)
	at com.atlassian.bamboo.plugins.git.GitOperationHelper.obtainLatestRevision(GitOperationHelper.java:294)
	at com.atlassian.bamboo.plugins.git.GitRepository.collectChangesSinceLastBuild(GitRepository.java:214)
	at com.atlassian.bamboo.v2.trigger.DefaultChangeDetectionManager$1.call(DefaultChangeDetectionManager.java:386)
	at com.atlassian.bamboo.v2.trigger.DefaultChangeDetectionManager$1.call(DefaultChangeDetectionManager.java:383)
	at com.atlassian.bamboo.executor.RetryingTaskExecutor.rerun(RetryingTaskExecutor.java:100)
	... 42 more