watcher: allow immediately released or already released semaphores to…

… trickle down into future wait logic

devel/include/wtr/watcher-/watch.hpp

@@ -88,7 +88,7 @@ class watch {
 
   inline auto close() noexcept -> bool
   {
-    return this->living.release() != sb::state::pending
+    return this->living.release() != sb::state::error
         && this->watching.valid() && this->watching.get();
   };