assiging the version to -1 in the descriptor when the BAT is unloaded is not correct, as the descriptor stays cached.
assiging the version to -1 in the descriptor when the BAT is unloaded is
not correct, as the descriptor stays cached.

This means that BATsavedesc does not save the descriptor anymore
after it is relaoded, causing the desc file to go missing after
a succesful commit => CORRUPT REPOSITORY

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb