drm/panel: himax-hx83102: Add a check to prevent NULL pointer dereference

drm/panel: himax-hx83102: Add a check to prevent NULL pointer dereference

drm_mode_duplicate() could return NULL due to lack of memory,
which will then call NULL pointer dereference. Add a check to
prevent it.

Fixes: 0ef94554dc40 ("drm/panel: himax-hx83102: Break out as separate driver")
Signed-off-by: Zhang Zekun <zhangzekun11@huawei.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20241025073408.27481-3-zhangzekun11@huawei.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241025073408.27481-3-zhangzekun11@huawei.com