[Bug c++/125904] contracts: assertion not evaluated if only statement in loop body

[ville.voutilainen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125904

--- Comment #1 from Ville Voutilainen <ville.voutilainen at gmail dot com> ---
Created attachment 64805
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=64805&action=edit
Patch, without test changes

This seems to cure it.