ConcurrentModificationException in THashIterator
I've just caught the following exception:
```
null
java.util.ConcurrentModificationException
	at gnu.trove.THashIterator.nextIndex(THashIterator.java:83)
	at gnu.trove.TIterator.moveToNextIndex(TIterator.java:88)
	at gnu.trove.THashIterator.next(THashIterator.java:67)
	at com.intellij.util.containers.RefHashMap$EntrySet$1.hasNext(RefHashMap.java:308)
	at com.intellij.util.containers.RefHashMap$EntrySet.isEmpty(RefHashMap.java:340)
	at com.intellij.util.containers.RefHashMap.isEmpty(RefHashMap.java:205)
	at com.intellij.util.containers.WeakHashMap.isEmpty(WeakHashMap.java:36)
	at mobi.hsz.idea.gitignore.IgnoreManager.isFileTracked(IgnoreManager.java:369)
	at mobi.hsz.idea.gitignore.projectView.IgnoreViewNodeDecorator.decorate(IgnoreViewNodeDecorator.java:89)
	at com.intellij.ide.projectView.impl.nodes.AbstractPsiBasedNode.a(AbstractPsiBasedNode.java:169)
	at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:934)
	at com.intellij.ide.projectView.impl.nodes.AbstractPsiBasedNode.update(AbstractPsiBasedNode.java:139)
	at com.intellij.ide.util.treeView.PresentableNodeDescriptor.getUpdatedPresentation(PresentableNodeDescriptor.java:88)
	at com.intellij.ide.util.treeView.PresentableNodeDescriptor.update(PresentableNodeDescriptor.java:41)
	at com.intellij.ide.util.treeView.AbstractTreeBuilder.updateNodeDescriptor(AbstractTreeBuilder.java:577)
	at com.intellij.ide.util.treeView.AbstractTreeUi$22.perform(AbstractTreeUi.java:935)
	at com.intellij.ide.util.treeView.TreeRunnable.run(TreeRunnable.java:36)
	at com.intellij.ide.util.treeView.AbstractTreeUi.execute(AbstractTreeUi.java:1856)
	at com.intellij.ide.util.treeView.AbstractTreeUi.update(AbstractTreeUi.java:931)
	at com.intellij.ide.util.treeView.AbstractTreeUi.update(AbstractTreeUi.java:883)
	at com.intellij.ide.util.treeView.AbstractTreeUi.access$1600(AbstractTreeUi.java:64)
	at com.intellij.ide.util.treeView.AbstractTreeUi$24$1.run(AbstractTreeUi.java:1092)
	at com.intellij.ide.util.treeView.AbstractTreeUi.execute(AbstractTreeUi.java:1835)
	at com.intellij.ide.util.treeView.AbstractTreeUi.access$5200(AbstractTreeUi.java:64)
	at com.intellij.ide.util.treeView.AbstractTreeUi$33.perform(AbstractTreeUi.java:1801)
	at com.intellij.ide.util.treeView.TreeRunnable.run(TreeRunnable.java:36)
	at com.intellij.ide.util.treeView.AbstractTreeUi.executeYieldingRequest(AbstractTreeUi.java:2090)
	at com.intellij.ide.util.treeView.AbstractTreeUi.access$5800(AbstractTreeUi.java:64)
	at com.intellij.ide.util.treeView.AbstractTreeUi$36$1.perform(AbstractTreeUi.java:2002)
	at com.intellij.ide.util.treeView.TreeRunnable.run(TreeRunnable.java:36)
	at com.intellij.ide.util.treeView.AbstractTreeBuilder.runOnYeildingDone(AbstractTreeBuilder.java:433)
	at com.intellij.ide.util.treeView.AbstractTreeUi.runOnYieldingDone(AbstractTreeUi.java:2185)
	at com.intellij.ide.util.treeView.AbstractTreeUi$36.perform(AbstractTreeUi.java:1997)
	at com.intellij.ide.util.treeView.TreeRunnable.run(TreeRunnable.java:36)
	at com.intellij.ide.util.treeView.AbstractTreeBuilder.lambda$new$0(AbstractTreeBuilder.java:51)
	at com.intellij.util.containers.TransferToEDTQueue.processNext(TransferToEDTQueue.java:102)
	at com.intellij.util.containers.TransferToEDTQueue.access$300(TransferToEDTQueue.java:37)
	at com.intellij.util.containers.TransferToEDTQueue$1.run(TransferToEDTQueue.java:57)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:762)
	at java.awt.EventQueue.access$500(EventQueue.java:98)
	at java.awt.EventQueue$3.run(EventQueue.java:715)
	at java.awt.EventQueue$3.run(EventQueue.java:709)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:732)
	at com.intellij.ide.IdeEventQueue.e(IdeEventQueue.java:821)
	at com.intellij.ide.IdeEventQueue._dispatchEvent(IdeEventQueue.java:649)
	at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:365)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
```

IntelliJ IDEA 2017.2.1
Build #IU-172.3544.35, built on July 31, 2017

JRE: 1.8.0_152-release-915-b6 x86_64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Mac OS X 10.12.6