c++: ICE with generic lambda and pack expansion [PR115425]

c++: ICE with generic lambda and pack expansion [PR115425]

In r13-272 we hardened the *_PACK_EXPANSION and *_ARGUMENT_PACK macros.
That trips up here because make_pack_expansion returns error_mark_node
and we access that with PACK_EXPANSION_LOCAL_P.

	PR c++/115425

gcc/cp/ChangeLog:

	* pt.cc (tsubst_pack_expansion): Return error_mark_node if
	make_pack_expansion doesn't work out.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/lambda-generic12.C: New test.