Update VE core submodule to master (8b78c2b)

New changes:
388a930 Followup b8d8a5b: fix getNativeRange() in null selection case
c049570 ve.ui.CommentInspector: Update size when the textarea gets resized

Change-Id: Idaf49529c65ed858a11c27b0d9ec0dd55488c9a7