Slimeblock will show missing textuer when placed with fill command

i wrote fill command in a commandblock but instead of 0 for the datatag i put 1, and it acted like a wool block would act. White wool becomes orange , slime block turns into missing texture. (still acts bounces and slows down entities)

Steps to Reproduce:
1.Place Command Block
2. /fill ~ ~1 ~ ~5 ~1 ~5 slime_block 1