uxtheme/tests: Add a test for SetWindowTheme/OpenThemeData sequence.

dlls/uxtheme/tests/system.c

@@ -558,6 +558,16 @@ static void test_OpenThemeData(void)
 
     /* Only do the next checks if we have an active theme */
 
+    hRes = SetWindowTheme(hWnd, L"explorer", NULL);
+    ok(hRes == S_OK, "Got unexpected hr %#lx.\n", hRes);
+    SetLastError(0xdeadbeef);
+    hTheme = OpenThemeData(hWnd, L"explorer::treeview");
+    todo_wine
+    ok(!hTheme, "OpenThemeData() should fail\n");
+    todo_wine
+    ok(GetLastError() == E_PROP_ID_UNSUPPORTED, "Got unexpected %#lx.\n", GetLastError());
+    SetWindowTheme(hWnd, NULL, NULL);
+
     SetLastError(0xdeadbeef);
     hTheme = OpenThemeData(hWnd, L"dead::beef;explorer::treeview");
     todo_wine