[NTG-context] \tfx or \tfxx is fail with nonintegral fonts size

Hi all, I find the "\tfx" or "\tfxx" is fail in nonintegral fonts size with latest beta (MKIV), but the "\small" was worked. example: \starttext \switchtobodyfont[15.01pt] \tfxx test \switchtobodyfont[15pt] \tfx test \switchtobodyfont[15.01pt] \small test \stoptext -- Best regards, Huang Ze