CursorWrapHelper: Do not crash on Wayland.
According to https://bugs.kde.org/show_bug.cgi?id=437334 the cursor position is not necessarily known on Wayland. That would trigger the Q_ASSERT_X, so this patch removes it. This does not solve the problem that we can not wrap the cursor, but it prevents crashing Okular if using the debug build on Wayland.