"Unable to save settings"

I keep getting "Unable to save settings" when I start up Idea Ultimate 2017.3. I've tried renaming my config dir so that a new one would be created, but that doesn't help.

I saw some other posts with similar message, but my idea.log is showing a different exception stack trace. 

2018-11-20 20:03:41,930 [ 445383] WARN - mponents.impl.stores.StoreUtil - Save settings failed
java.lang.RuntimeException: java.lang.Exception: Cannot get VcsDirectoryMappings component state
at com.intellij.util.ExceptionUtil.rethrow(ExceptionUtil.java:171)
at com.intellij.util.lang.CompoundRuntimeException.throwIfNotEmpty(CompoundRuntimeException.java:153)
at com.intellij.configurationStore.ComponentStoreImpl.save(ComponentStoreImpl.kt:198)
at com.intellij.openapi.components.impl.stores.StoreUtil.save(StoreUtil.java:49)
at com.intellij.openapi.project.impl.ProjectImpl.save(ProjectImpl.java:349)
at com.intellij.openapi.components.impl.stores.StoreUtil.saveDocumentsAndProjectsAndApp(StoreUtil.java:126)
at com.intellij.openapi.application.impl.ApplicationImpl.saveAll(ApplicationImpl.java:1413)
at com.intellij.ide.SaveAndSyncHandlerImpl.saveProjectsAndDocuments(SaveAndSyncHandlerImpl.java:126)
at com.intellij.ide.SaveAndSyncHandlerImpl$2.a(SaveAndSyncHandlerImpl.java:94)
at com.intellij.openapi.application.TransactionGuardImpl.a(TransactionGuardImpl.java:88)
at com.intellij.openapi.application.TransactionGuardImpl.a(TransactionGuardImpl.java:111)
at com.intellij.openapi.application.TransactionGuardImpl.submitTransaction(TransactionGuardImpl.java:120)
at com.intellij.openapi.application.TransactionGuard.submitTransaction(TransactionGuard.java:122)
at com.intellij.ide.SaveAndSyncHandlerImpl$2.onFrameDeactivated(SaveAndSyncHandlerImpl.java:92)
at com.intellij.ide.FrameStateManagerImpl.a(FrameStateManagerImpl.java:84)
at com.intellij.ide.FrameStateManagerImpl.access$500(FrameStateManagerImpl.java:32)
at com.intellij.ide.FrameStateManagerImpl$2.a(FrameStateManagerImpl.java:70)
at com.intellij.util.concurrency.QueueProcessor.runSafely(QueueProcessor.java:246)
at com.intellij.util.Alarm$Request.runSafely(Alarm.java:417)
at com.intellij.util.Alarm$Request.access$700(Alarm.java:344)
at com.intellij.util.Alarm$Request$1.run(Alarm.java:384)
at com.intellij.openapi.application.TransactionGuardImpl$2.run(TransactionGuardImpl.java:315)
at com.intellij.openapi.application.impl.LaterInvocator$FlushQueue.a(LaterInvocator.java:424)
at com.intellij.openapi.application.impl.LaterInvocator$FlushQueue.run(LaterInvocator.java:407)
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.a(IdeEventQueue.java:822)
at com.intellij.ide.IdeEventQueue._dispatchEvent(IdeEventQueue.java:650)
at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:366)
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)
Caused by: java.lang.Exception: Cannot get VcsDirectoryMappings component state
at com.intellij.configurationStore.ComponentStoreImpl.save(ComponentStoreImpl.kt:165)
... 38 more
Caused by: org.jdom.IllegalDataException: The data "null" is not legal for a JDOM attribute: A null is not a legal XML value.
at org.jdom.Attribute.setValue(Attribute.java:491)
at org.jdom.Attribute.<init>(Attribute.java:228)
at org.jdom.Attribute.<init>(Attribute.java:251)
at org.jdom.Element.setAttribute(Element.java:1160)