Uncaught Mercury exception:
Software Error: string.format: The first conversion specifier, which uses specifier character `s', is missing its input.
Stack dump follows:
	mercury__exception:-throw_impl_1_p_0/1-fun-0-/1
	mercury__string:format_string_to_specifiers_5_p_0/2
	mercury__string:format_3_p_0/2
	mercury__io:format_4_p_0/2
	string_format_test_3:mercury__main_wrapper/0