isl_output.c: print_union_pw_aff_body: fix double free on error path
isl_output.c: print_union_pw_aff_body: fix double free on error path

Signed-off-by: Sven Verdoolaege <235c10dd23b819f81cdc9756a251746bc184cab6@gmail.com>

Meinersbur/isl,Meinersbur/isl,Meinersbur/isl,Meinersbur/isl