openmp: Don't ICE on detach clause with erroneous decl [PR98742]

openmp: Don't ICE on detach clause with erroneous decl [PR98742]

Similarly to how we handle erroneous operands to e.g. allocate clause,
this change just removes those clauses instead of accessing TYPE_MAIN_VARIANT
of its type, which doesn't work on error_mark_node.  Also, just for good
measure, bails out if TYPE_NAME is NULL.

2021-01-20  Jakub Jelinek  <jakub@redhat.com>

	PR c++/98742
	* semantics.c (finish_omp_clauses) <case OMP_CLAUSE_DETACH>: If
	error_operand_p, remove clause without further checking.  Check
	for non-NULL TYPE_NAME.

	* c-c++-common/gomp/task-detach-2.c: New test.

(cherry picked from commit 7ab1abf3b82a3bcfff9b7bc596166fef6a0d83ab)