fix generation of key events with Alt pressed broken by r59369 (see #626)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@59406 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/treectrl.cpp

@@ -3308,8 +3308,8 @@ bool wxTreeCtrl::MSWOnNotify(int idCtrl, WXLPARAM lParam, WXLPARAM *result)
                 // fabricate the lParam and wParam parameters sufficiently
                 // similar to the ones from a "real" WM_KEYDOWN so that
                 // CreateKeyEvent() works correctly
-                return MSWHandleTreeKeyDownEvent(info->wVKey,
+                return MSWHandleTreeKeyDownEvent(
-                                                 wxIsAltDown() << 16);
+                        info->wVKey, (wxIsAltDown() ? KF_ALTDOWN : 0) << 16);
             }
             break;