[Editing] Add null check in |DeleteSelectionCommand::removeRedundantBlocks()|

third_party/WebKit/Source/core/editing/commands/DeleteSelectionCommand.cpp

 /*
  * Copyright (C) 2005 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 1004 matching lines @@
   m_referenceMovePosition = Position();
 }
 
 // This method removes div elements with no attributes that have only one child
 // or no children at all.
 void DeleteSelectionCommand::removeRedundantBlocks(EditingState* editingState) {
   Node* node = m_endingPosition.computeContainerNode();
   Element* rootElement = rootEditableElement(*node);
 
   while (node != rootElement) {
+    ABORT_EDITING_COMMAND_IF(!node);
     if (isRemovableBlock(node)) {
       if (node == m_endingPosition.anchorNode())
         updatePositionForNodeRemovalPreservingChildren(m_endingPosition, *node);
 
       CompositeEditCommand::removeNodePreservingChildren(node, editingState);
       if (editingState->isAborted())
         return;
       node = m_endingPosition.anchorNode();
     } else {
       node = node->parentNode();
@@ skipping 191 matching lines @@
   visitor->trace(m_deleteIntoBlockquoteStyle);
   visitor->trace(m_startRoot);
   visitor->trace(m_endRoot);
   visitor->trace(m_startTableRow);
   visitor->trace(m_endTableRow);
   visitor->trace(m_temporaryPlaceholder);
   CompositeEditCommand::trace(visitor);
 }
 
 }  // namespace blink