patch 8.1.1843: might be freeing memory that was not allocated

Problem:    Might be freeing memory that was not allocated.
Solution:   Have next_fenc() set the fenc_alloced flag. (closes #4804)
diff --git a/src/version.c b/src/version.c
index 568852b..5741d5f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1843,
+/**/
     1842,
 /**/
     1841,