shell32: Avoid crash on WM_WINDOWPOSCHANGING in BrsFolderDlgProc.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=48510
Signed-off-by: Roman Pišl <rpisl@seznam.cz>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>
(cherry picked from commit a102671720)
Signed-off-by: Michael Stefaniuc <mstefani@winehq.org>

dlls/shell32/brsfolder.c

@@ -1109,6 +1109,8 @@ static INT_PTR CALLBACK BrsFolderDlgProc( HWND hWnd, UINT msg, WPARAM wParam,
         return BrsFolder_OnCreate( hWnd, (browse_info*) lParam );
 
     info = GetPropW( hWnd, szBrowseFolderInfo );
+    if (!info)
+        return FALSE;
 
     switch (msg)
     {