I wanted to see what would happen if I asked to improve my shield even though I didn't have another mythril shard.
I had 2 shields at the time, the base shield and the tower shield.
Smith gave the correct response, that he could do it, but not without a shard, but then the game hardlocked on the shields selection.
In case that matters, playing in Goomba emulator, in turn, loading/running off EZ Flash Omega, and then on authentic GBA SP