i'me just using a sprite entity (smoke)

i typed out the whole path correctly, i tried browsing to it but didn't work neither.

since i can see the sprite in hammer, i guess it's correct.
i can see the sprite in hammer but the map won't load.

ERROR: "Mod_NumForName" : sprites/null.spr not found

i'm sorry if this has been posted earlier, i searched but failed to find.
i'me kinda stuck so please help :(

"desperate"