isl_basic_set_remove_equalities: always set transformation matrices
When the input to isl_basic_set_remove_equalities does not satisfy
any equalities, the function would set the transformation matrices
to NULL, which could be treated as an error condition by the caller.
Even though isl_basic_set_remove_equalities should never actually
get called under these circumstances, make sure the transformation
matrices are always assigned proper values just in case.
Signed-off-by: Sven Verdoolaege <skimo@kotnet.org>