PR c/66415
	* c-format.c (location_from_offset): Return LOC if LINE is null.

	* line-map.c (linemap_position_for_loc_and_offset): Remove
	linemap_assert_fails; reverse conditions.

	* gcc.dg/cpp/pr66415-1.c: New test.
	* gcc.dg/cpp/pr66415-2.c: New test.

From-SVN: r224236