Get a IndexEntryResolveUndo by index.
Note that the returned IndexEntryResolveUndo is _only_ valid as long as:
1) The associated index has been closed 2) The entry has not been removed (see remove ) 3) The index has not been refreshed (see read)
| this | |
| idx |
the index of the entry. |
|
a IndexEntryResolveUndo or null. |