If `Ns' is specified on its own line, it should be ignored. This is

shitty groff behaviour.  Do the same, but raise a warning to this
effect.  This from a TODO noted by schwarze@.

1 files changed, 2 insertions, 0 deletions

diff --git a/mdoc.7 b/mdoc.7
index 9e4eb56e..3adfb256 100644
--- a/mdoc.7
+++ b/mdoc.7
@@ -2203,6 +2203,8 @@ Suppress a space.
 Following invocation, text is interpreted as free-form text until a
 macro is encountered.
 .Pp
+This has no effect when invoked at the start of a macro line.
+.Pp
 Examples:
 .Dl \&.Fl o \&Ns \&Ar output
 .Pp