patch 8.2.3916: no error for passing an invalid line number to append()

Problem:    No error for passing an invalid line number to append().
Solution:   In Vim9 script check for a non-negative number. (closes #9417)
diff --git a/src/version.c b/src/version.c
index 7b454a6..944b1f6 100644
--- a/src/version.c
+++ b/src/version.c
@@ -750,6 +750,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3916,
+/**/
     3915,
 /**/
     3914,