Fixed incorrectly named variable, and use EFFECTIVE-SLOTS reader.
Fixed incorrectly named variable, and use EFFECTIVE-SLOTS reader.

clasp-developers/SICL,clasp-developers/SICL,clasp-developers/SICL,vtomole/SICL,vtomole/SICL,vtomole/SICL,vtomole/SICL,clasp-developers/SICL