%on_error_reduce on start symbol causes assertion failure
(Reported by Pierre Courtieu.) The following grammar is problematic:
%token TRUE
%start <unit> foo
%on_error_reduce foo
%%
foo: TRUE {()}
It causes an assertion failure both in the code back-end and in the table back-end:
$ menhir courtieu.mly --table
Fatal error: exception File "src/tableBackend.ml", line 509, characters 12-18: Assertion failed
$ menhir courtieu.mly
Fatal error: exception File "src/codeBackend.ml", line 930, characters 6-12: Assertion failed