Create -unmatched descendents incorrect number

[rw251]

Search for warfarin - 4 unmatched descendents. Add Marevan from unmatched desc tab. Number of unmatched desc drops to -3.

[richard-uk1]

I've seen this as well, meaning I can debug it if you like.

[rw251]

It's very low priority so I wouldn't bother. Also this will be superceded when we switch to a tree view rather than a table.