TupleBatch: more precondition checking
TupleBatch: more precondition checking

Signed-off-by: Daniel Halperin <1a02732a15f637c31107256cbee5819e36aa7c67@cs.washington.edu>

uwescience/myria,jamesmarva/myria,uwescience/myria,uwescience/myria,bsalimi/myria,jamesmarva/myria,bsalimi/myria,jamesmarva/myria,bsalimi/myria