Reviewed by Adam.

        Fix for rdar://problem/5021127 

        Need to add null check to node -- original Obj-C didn't need 
        the null check due to the Obj-C null messaging semantics

        * editing/Editor.cpp:
        (WebCore::Editor::shouldInsertFragment):

Layout tests:
        Layout test for rdar://problem/5021127

        * fast/events/standalone-image-drag-to-editable-expected.checksum: Added.
        * fast/events/standalone-image-drag-to-editable-expected.png: Added.
        * fast/events/standalone-image-drag-to-editable-expected.txt: Added.
        * fast/events/standalone-image-drag-to-editable.html: Added.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@19870 268f45cc-cd09-0410-ab3c-d52691b4dbfc