patch 9.0.1727: minor problems with the teapot

Problem: minor problems with the teapot()
Solution: remove the null check, update documentation

Update the builtin-function-list entry. (It implicitly returns 0, but such
functions usually use "none")

Also, tv_get_string_strict() can not return NULL, so remove that check

closes: #12647

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Sean Dewar <seandewar@users.noreply.github.com>

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1727,
 /**/
     1726,
 /**/