[libgee] Fix item count decrementation on removal in AbstractMultiSet

[Didier Villevalois <dvillevalois src gnome org>]

commit 35c7ad615900c0d68399225e6ceb8549639e3006
Author: Didier 'Ptitjes <ptitjes free fr>
Date:   Thu Sep 24 00:57:51 2009 +0200

    Fix item count decrementation on removal in AbstractMultiSet

 gee/abstractmultiset.vala |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/gee/abstractmultiset.vala b/gee/abstractmultiset.vala
index 83b39e5..e046620 100644
--- a/gee/abstractmultiset.vala
+++ b/gee/abstractmultiset.vala
@@ -137,6 +137,7 @@ public abstract class Gee.AbstractMultiSet<G> : AbstractCollection<G>, MultiSet<
 			if (_pending == 0) {
 				_iter.unset ();
 			}
+			_set._nitems--;
 			_removed = true;
 		}
 	}