riched20: hWnd validity test in window procedure

[Krzysztof Foltman]

ChangeLog:
  * Added hWnd validity check to work around buggy apps (bug# 4452)

This patch is based on Phil Krylov's one, with two differences: it 
checks the handle even before trying to call GetWindowLong, and it 
checks for invalid window handle, not just NULL.

Krzysztof
-------------- next part --------------
diff --git a/dlls/riched20/editor.c b/dlls/riched20/editor.c
index 9a2b966..50527ca 100644
--- a/dlls/riched20/editor.c
+++ b/dlls/riched20/editor.c
@@ -1393,8 +1394,16 @@ get_msg_name(UINT msg)
  */
 LRESULT WINAPI RichEditANSIWndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) {
   SCROLLINFO si;
-  ME_TextEditor *editor = (ME_TextEditor *)GetWindowLongW(hWnd, 0);
-  
+  ME_TextEditor *editor;
+
+  /* Some braindead subclassed window procedures call the original procedure
+   * with NULL or invalid window handle */
+  if (!hWnd || !IsWindow(hWnd)) {
+    ERR("RichEditANSIWndProc called with invalid hWnd %p - application bug?\n", hWnd);
+    return 0; 
+  }
+    
+  editor = (ME_TextEditor *)GetWindowLongW(hWnd, 0);
   TRACE("hWnd %p msg %04x (%s) %08x %08lx\n",
         hWnd, msg, get_msg_name(msg), wParam, lParam);