Bug 341127: Fix the remaining invalid read in rc4_wordconv. r=sleevi.
Bug 341127: Fix the remaining invalid read in rc4_wordconv. r=sleevi.

ekr/nss-old,nmav/nss,ekr/nss-old,nmav/nss,ekr/nss-old,ekr/nss-old,ekr/nss-old,nmav/nss,ekr/nss-old,nmav/nss,ekr/nss-old,nmav/nss,nmav/nss,nmav/nss