Fills in path and focus_column with the current path and focus column.
If the cursor isn’t currently set, then *path will be null. If no column currently has
focus, then *focus_column will be null.
The returned `GtkTreePath` must be freed with free when you are done with it.
| this |
A `GtkTreeView` |
| path |
A pointer to be filled with the current cursor path |
| focus_column |
A pointer to be filled with the current focus column |