Null stateNode after unmount (#17666)

Author: Brian Vaughn

packages/legacy-events/ReactControlledComponent.js

@@ -33,8 +33,12 @@ function restoreStateOfTarget(target) {
     'setRestoreImplementation() needs to be called to handle a target for controlled ' +
       'events. This error is likely caused by a bug in React. Please file an issue.',
   );
-  const props = getFiberCurrentPropsFromNode(internalInstance.stateNode);
-  restoreImpl(internalInstance.stateNode, internalInstance.type, props);
+  const stateNode = internalInstance.stateNode;
+  // Guard against Fiber being unmounted.
+  if (stateNode) {
+    const props = getFiberCurrentPropsFromNode(stateNode);
+    restoreImpl(internalInstance.stateNode, internalInstance.type, props);
+  }
 }
 
 export function setRestoreImplementation(

packages/react-reconciler/src/ReactFiberCommitWork.js

@@ -905,6 +905,7 @@ function detachFiber(current: Fiber) {
   current.lastEffect = null;
   current.pendingProps = null;
   current.memoizedProps = null;
+  current.stateNode = null;
   if (alternate !== null) {
     detachFiber(alternate);
   }