You can do this but you'll lose all your hacks and installed games that did you did not buy. The behavior of not booting without the SD card is completely normal and a side-effect of installing A9LH. You can however do one more step and make it so it will boot without the SD card. Just follow this guide to do so: https://www.reddit.com/r/3dshacks/comments/57zm0b/how_to_install_sdless_a9lh_with_luma_3ds_nightly/how do i revert back to normal sysnand? as in, boot into 3ds without memory card inserted is possible