I have had the 'String index out of range' error several times when I started to work with Zuti's actors tool.
If your error is the same one I used to have the solution is simple.
Take care that the edited entries are lined up and no empty space between the lines.
And if I remember correctly no empty lines after the last entry in your extracted text file.
Example:
WRONG 15585_bld House$HorseLightbrown 1 265270.38 150537.20 4.95
15586_bld House$SEhouse30 1 265278.06 150532.20 354.96
15587_bld House$hitching_post_003 1 265270.72 150535.64 264.96
15588_bld House$HorseBlack 1 264986.44 150618.42 119.97
15589_bld House$HorseWhite 1 264987.28 150620.08 109.98
15590_bld House$hitching_post_003 1 264985.69 150620.08 19.98
WRONG 15585_bld House$HorseLightbrown 1 265270.38 150537.20 4.95
15586_bld House$SEhouse30 1 265278.06 150532.20 354.96
15587_bld House$hitching_post_003 1 265270.72 150535.64 264.96
15588_bld House$HorseBlack 1 264986.44 150618.42 119.97
15589_bld House$HorseWhite 1 264987.28 150620.08 109.98
15590_bld House$hitching_post_003 1 264985.69 150620.08 19.98
RIGHT 15585_bld House$HorseLightbrown 1 265270.38 150537.20 4.95
15586_bld House$SEhouse30 1 265278.06 150532.20 354.96
15587_bld House$hitching_post_003 1 265270.72 150535.64 264.96
15588_bld House$HorseBlack 1 264986.44 150618.42 119.97
15589_bld House$HorseWhite 1 264987.28 150620.08 109.98
15590_bld House$hitching_post_003 1 264985.69 150620.08 19.98
By the way, you do not have to replace deleted objects with other objects to keep the numbering consecutive.
During creating the new inBuildings file it gets renumbered in a consecutive order.
As long as you keep the entries lined up and no empty lines.