After installation of this mod, useful tooltips from Nullius mod are replaced just with stack size tooltips.

Steps to reproduce:
1. Add https://mods.factorio.com/mod/nullius mod
2. Start freeplay game and look at the stone logistic request which displays "State: Solid (void in 4)"
3. Save the game
4. Add Stack Size Tooltip mod
5. Reload the game
6. Observe that same stone logistic request has "Stack size: 50" tooltip and previous description is not extended but erased instead.

Not sure if that is an intended behaviour or a bug, but it would be really nice to have existing item description to be extended with stack size instead of replaced by it.

Thanks for the report.
I'll take a look at it.

Created fix myself, clonning your github repository; tested with EN version and SpaceExploration mod and no problems found.
Pull request placed.
Strongly recommend to other players to download via standard game mechanic once @SmetDenis releases (hopefully) this fix as new version; for the impatient it is immediately available as the (only) release under https://github.com/pmendl/Factorio-Stack-Size-Tooltip/releases/tag/V1.0.1
(Remind you, that the zip file has to be named as "stack-size-tooltip_1.0.1.zip to be accepted by the game.)

Thank you!

Approved and merged.