patch 9.1.0399: block_editing errors out when using del

Problem:  block_editing errors out when using del
          (@Jamarley)
Solution: Change ins_len from size_t to int and
          properly check that it doesn't become negative

There is a check in os.c that verifies that `ins_len` does not become
negative:
```
if (pre_textlen >= 0 && (ins_len = len - pre_textlen - offset) > 0)
```
However this only works, if ins_len can actually become negative and
unfortunately, ins_len has been declared as `size_t` so instead of
becoming negative it will wrap around and be very large.

So let's define it as integer, after which the condition above
properly catches this condition.

fixes: #14734
closes: #14735

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index ba03c1a..06f0c62 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    399,
+/**/
     398,
 /**/
     397,