ReleaseCapture on lbuttondown if the cursor is outside an item, just
like the native one does.

dlls/comctl32/listview.c

diff --git a/dlls/comctl32/listview.c b/dlls/comctl32/listview.c
index 7889ceb..26bbede 100644
--- a/dlls/comctl32/listview.c
+++ b/dlls/comctl32/listview.c
@@ -7944,6 +7944,7 @@
   {
     /* remove all selections */
     LISTVIEW_DeselectAll(infoPtr);
+    ReleaseCapture();
   }
 
   return 0;