user32: Handle NULL rectangles in WM_NCCALCSIZE.

dlls/user32/nonclient.c

@@ -417,6 +417,9 @@ LRESULT NC_HandleNCCalcSize( HWND hwnd, RECT *winRect )
     LONG style = GetWindowLongW( hwnd, GWL_STYLE );
     LONG exStyle = GetWindowLongW( hwnd, GWL_EXSTYLE );
 
+    if (winRect == NULL)
+        return 0;
+
     if (cls_style & CS_VREDRAW) result |= WVR_VREDRAW;
     if (cls_style & CS_HREDRAW) result |= WVR_HREDRAW;
 

dlls/user32/tests/win.c

@@ -781,6 +781,7 @@ static void test_nonclient_area(HWND hwnd)
     RECT rc_window, rc_client, rc;
     BOOL menu;
     BOOL is_win9x = GetWindowLongPtrW(hwnd, GWLP_WNDPROC) == 0;
+    LRESULT ret;
 
     style = GetWindowLongA(hwnd, GWL_STYLE);
     exstyle = GetWindowLongA(hwnd, GWL_EXSTYLE);
@@ -809,6 +810,10 @@ static void test_nonclient_area(HWND hwnd)
     trace("calc client: (%d,%d)-(%d,%d)\n", rc.left, rc.top, rc.right, rc.bottom);
     ok(EqualRect(&rc, &rc_client), "client rect does not match: style:exstyle=0x%08x:0x%08x, menu=%d\n", style, exstyle, menu);
 
+    /* NULL rectangle shouldn't crash */
+    ret = DefWindowProcA(hwnd, WM_NCCALCSIZE, 0, 0);
+    ok(ret == 0, "NULL rectangle returned %ld instead of 0\n", ret);
+
     /* Win9x doesn't like WM_NCCALCSIZE with synthetic data and crashes */;
     if (is_win9x)
 	return;