gdb/

	gdb/
	* exceptions.c (throw_exception): Don't disable the current
	display.
	* printcmd.c (disable_current_display_cleanup): New function.
	(do_one_display): Install a cleanup to disable the current display
	if doing the display throws.

	gdb/testsuite/
	* gdb.trace/unavailable.exp (test_maybe_regvar_display): New
	procedure.
	(gdb_collect_args_test, gdb_collect_locals_test): Use it.