patch 9.1.0477: block_editing errors out when using <enter>

Problem:  block_editing errors out when using <enter>
          (Ali Rizvi-Santiago, after v9.1.0274)
Solution: Change ins_len from size_t to int so that the test
          if ins_len is negative actually works properly

Add a test, so that this doesn't regress.

fixes: #14960

Signed-off-by: Christian Brabandt <cb@256bit.org>

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    477,
 /**/
     476,
 /**/