user: Call SetLastError in CreateWindowEx when WS_CHILD is set with no parent.

dlls/user/tests/win.c

@@ -140,7 +140,7 @@ static void test_parent_owner(void)
     SetLastError(0xdeadbeef);
     test = CreateWindowExA(0, "ToolWindowClass", "Tool window 1",
                            WS_CHILD, 0, 0, 100, 100, 0, 0, 0, NULL );
-    todo_wine ok( GetLastError() == ERROR_TLW_WITH_WSCHILD, "CreateWindowExA should call SetLastError\n" );
+    ok( GetLastError() == ERROR_TLW_WITH_WSCHILD, "CreateWindowExA should call SetLastError\n" );
     ok( !test, "WS_CHILD without parent created\n" );
 
     /* desktop window */

dlls/user/win.c

@@ -995,6 +995,7 @@ static HWND WIN_CreateWindowEx( CREATESTRUCTA *cs, ATOM classAtom, UINT flags )
         if ((cs->style & (WS_CHILD|WS_POPUP)) == WS_CHILD)
         {
             WARN("No parent for child window\n" );
+            SetLastError(ERROR_TLW_WITH_WSCHILD);
             return 0;  /* WS_CHILD needs a parent, but WS_POPUP doesn't */
         }
         if (classAtom != LOWORD(DESKTOP_CLASS_ATOM))  /* are we creating the desktop itself? */