Added empty block and empty list decl as special cases so expl does not need to allow null.
Added empty block and empty list decl as special cases so expl does not need to allow null.

RTcmix/RTcmix,RTcmix/RTcmix,RTcmix/RTcmix,RTcmix/RTcmix,RTcmix/RTcmix,RTcmix/RTcmix