From the outset, top has tried to provide some minimal
garbage collection in support of forest view collapse.
For example, with every 'v' keystroke, a check is made
of the currently targeted pids.  If all were negative,
which means expanded, that Hide_pid array was emptied.

Recently, yet another efficiency was added wherein the
continuing scan for a targeted pid was terminated when
a match was found. But, one more inefficiency existed.

When a task which was subject to collapse under forest
view mode has disappeared (ended), repeatedly scanning
for such a pid with each iteration makes little sense.

So this commit will negate such targeted pids and thus
avoid scanning every current task looking for a match.
Then, if 'v' is ever stuck at some point in the future
there will be a chance to empty that Hide_pid[] array.

[ hopefully this will be a final tweak of the forest ]
[ view collapse stuff, but cross your fingers anyway ]

Signed-off-by: Jim Warner <james.warner@comcast.net>