Make execCommand("insertImage", false, "") not add a src attribute

Source/core/editing/EditorCommand.cpp

Index: Source/core/editing/EditorCommand.cpp
diff --git a/Source/core/editing/EditorCommand.cpp b/Source/core/editing/EditorCommand.cpp
index f21739a2dd0691a403624350bc8a40a7659c54f3..97873eb7c13f6a6baee3d77e4f1d49980ce2cb2b 100644
--- a/Source/core/editing/EditorCommand.cpp
+++ b/Source/core/editing/EditorCommand.cpp
@@ -517,7 +517,8 @@ static bool executeInsertImage(LocalFrame& frame, Event*, EditorCommandSource, c
 {
     ASSERT(frame.document());
     RefPtrWillBeRawPtr<HTMLImageElement> image = HTMLImageElement::create(*frame.document());
-    image->setSrc(value);
+    if (!value.isEmpty())
+        image->setSrc(value);
     return executeInsertElement(frame, image.release());
 }