[cache] Fix error handling. Manipulate the cache after a face is requested or a size is looked up successfully. Fixes #1270. * src/cache/ftcmanag.c (ftc_size_node_init, ftc_size_node_reset, ftc_face_node_init): Check for errors before accepting a change. * src/cache/ftcmru.c (FTC_MruList_New): Do nothing if reset fails.