When splitting selection into lines, destroy original selection last

This avoids an assertion failure due to destroying the last selection,
so we can reduce the noise and find code paths that destroy it
incorrectly.

src/text-editor.coffee

@@ -976,13 +976,13 @@ class TextEditor extends Model
         range = selection.getBufferRange()
         continue if range.isSingleLine()
 
-        selection.destroy()
         {start, end} = range
         @addSelectionForBufferRange([start, [start.row, Infinity]])
         {row} = start
         while ++row < end.row
           @addSelectionForBufferRange([[row, 0], [row, Infinity]])
         @addSelectionForBufferRange([[end.row, 0], [end.row, end.column]]) unless end.column is 0
+        selection.destroy()
       return
 
   # Extended: For each selection, transpose the selected text.