TREEVIEW_UpdateScrollBars() now copes with an empty tree.

dlls/comctl32/treeview.c

diff --git a/dlls/comctl32/treeview.c b/dlls/comctl32/treeview.c
index 3bf77aa..57d98c7 100644
--- a/dlls/comctl32/treeview.c
+++ b/dlls/comctl32/treeview.c
@@ -2690,14 +2690,23 @@
     if (vert)
     {
 	si.nPage = TREEVIEW_GetVisibleCount(infoPtr);
-	si.nPos  = infoPtr->firstVisible->visibleOrder;
-	si.nMax  = infoPtr->maxVisibleOrder - 1;
+       if ( si.nPage )
+       {
+           si.nPos  = infoPtr->firstVisible->visibleOrder;
+           si.nMax  = infoPtr->maxVisibleOrder - 1;
 
-	SetScrollInfo(hwnd, SB_VERT, &si, TRUE);
+           SetScrollInfo(hwnd, SB_VERT, &si, TRUE);
 
-	if (!(infoPtr->uInternalStatus & TV_VSCROLL))
-	    ShowScrollBar(hwnd, SB_VERT, TRUE);
-	infoPtr->uInternalStatus |= TV_VSCROLL;
+           if (!(infoPtr->uInternalStatus & TV_VSCROLL))
+               ShowScrollBar(hwnd, SB_VERT, TRUE);
+           infoPtr->uInternalStatus |= TV_VSCROLL;
+       }
+       else
+       {
+           if (infoPtr->uInternalStatus & TV_VSCROLL)
+               ShowScrollBar(hwnd, SB_VERT, FALSE);
+           infoPtr->uInternalStatus &= ~TV_VSCROLL;
+       }
     }
     else
     {