user32: don't crash if a WM_NCCREATE message is sent, with lParam=0.

[Louis. Lenders]

Skipped content of type multipart/alternative-------------- next part --------------
diff --git a/dlls/user32/defwnd.c b/dlls/user32/defwnd.c
index 06c10b2..dd7c884 100644
--- a/dlls/user32/defwnd.c
+++ b/dlls/user32/defwnd.c
@@ -772,6 +772,7 @@ LRESULT WINAPI DefWindowProcA( HWND hwnd
     switch(msg)
     {
     case WM_NCCREATE:
+        if(lParam) /* A simple test showed Windows checks for lParam being 0, but no last error is set */
         {
             CREATESTRUCTA *cs = (CREATESTRUCTA *)lParam;
             /* check for string, as static icons, bitmaps (SS_ICON, SS_BITMAP)
@@ -930,6 +931,7 @@ LRESULT WINAPI DefWindowProcW(
     switch(msg)
     {
     case WM_NCCREATE:
+        if(lParam) /* A simple test showed Windows checks for lParam being 0, but no last error is set */
         {
             CREATESTRUCTW *cs = (CREATESTRUCTW *)lParam;
             /* check for string, as static icons, bitmaps (SS_ICON, SS_BITMAP)