A treeview item may be TVI_ROOT.

diff --git a/dlls/comctl32/treeview.c b/dlls/comctl32/treeview.c
index bb3f9a8..82d3fb7 100644
--- a/dlls/comctl32/treeview.c
+++ b/dlls/comctl32/treeview.c
@@ -2039,6 +2039,8 @@
 	return (LRESULT)retval;
     }
 
+    if (wineItem == TVI_ROOT) wineItem = infoPtr->root;
+
     if (!TREEVIEW_ValidItem(infoPtr, wineItem))
 	return FALSE;