PR c++/28250
	* name-lookup.c (pushdecl_maybe_friend): Return early on
	error_mark_node.
	* except.c (expand_start_catch_block): Use error_mark_node instead
	of NULL_TREE for invalid decls.
	* parser.c (cp_parser_exception_declaration): Return error_mark_node
	on invalid catch parameter. Simplify.

	* g++.dg/eh/catch1.C: New test.
	* g++.dg/eh/catch2.C: New test.

From-SVN: r115516