Two fixes for grinder

* Fixes being able to click the grinder buttons while it's operating (can be exploited to eject beaker before grinding is finished), the grinder window is now correctly updated.

* Fixes death nettle not producing pacid upon grinding (fixes #6164), fixes novaflower not producing condensedcapsaicin (one of its reagents) upon grinding.
* Renaming "inuse" var to "operating" to avoid confusion with "in_use" var