Don't try to move non visible contents in "Indent" command

Source/core/editing/IndentOutdentCommand.cpp

 /*
  * Copyright (C) 2006, 2008 Apple 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 103 matching lines @@
         // Create a new blockquote and insert it as a child of the root editable element. We accomplish
         // this by splitting all parents of the current paragraph up to that point.
         targetBlockquote = createBlockElement();
         if (outerBlock == start.containerNode())
             insertNodeAt(targetBlockquote, start);
         else
             insertNodeBefore(targetBlockquote, outerBlock);
         startOfContents = VisiblePosition(positionInParentAfterNode(*targetBlockquote));
     }
 
-    moveParagraphWithClones(startOfContents, VisiblePosition(end), targetBlockquote.get(), outerBlock.get());
+    VisiblePosition endOfContents(end);
+    if (startOfContents.isNull() || endOfContents.isNull())
+        return;
+    moveParagraphWithClones(startOfContents, endOfContents, targetBlockquote.get(), outerBlock.get());
 }
 
 void IndentOutdentCommand::outdentParagraph()
 {
     VisiblePosition visibleStartOfParagraph = startOfParagraph(endingSelection().visibleStart());
     VisiblePosition visibleEndOfParagraph = endOfParagraph(visibleStartOfParagraph);
 
     Node* enclosingNode = enclosingNodeOfType(visibleStartOfParagraph.deepEquivalent(), &isListOrIndentBlockquote);
     if (!enclosingNode || !enclosingNode->parentNode()->rendererIsEditable()) // We can't outdent if there is no place to go!
         return;
@@ skipping 107 matching lines @@
 
 void IndentOutdentCommand::formatRange(const Position& start, const Position& end, const Position&, RefPtrWillBeRawPtr<Element>& blockquoteForNextIndent)
 {
     if (tryIndentingAsListItem(start, end))
         blockquoteForNextIndent = nullptr;
     else
         indentIntoBlockquote(start, end, blockquoteForNextIndent);
 }
 
 }