Check null position start of paragraph to move parameter in CompositeEditCommand::moveParagraph

Source/core/editing/CompositeEditCommand.cpp

Index: Source/core/editing/CompositeEditCommand.cpp
diff --git a/Source/core/editing/CompositeEditCommand.cpp b/Source/core/editing/CompositeEditCommand.cpp
index b7cdd68aa64943606b7a6a8274afb27129d2c66f..52d32ae6e8530172f1ca1c0c67f210b6e57c13fb 100644
--- a/Source/core/editing/CompositeEditCommand.cpp
+++ b/Source/core/editing/CompositeEditCommand.cpp
@@ -1147,7 +1147,7 @@ void CompositeEditCommand::moveParagraph(const VisiblePosition& startOfParagraph
 
 void CompositeEditCommand::moveParagraphs(const VisiblePosition& startOfParagraphToMove, const VisiblePosition& endOfParagraphToMove, const VisiblePosition& destination, bool preserveSelection, bool preserveStyle, Node* constrainingAncestor)
 {
-    if (startOfParagraphToMove == destination)
+    if (startOfParagraphToMove == destination || startOfParagraphToMove.isNull())
         return;
 
     int startIndex = -1;