patch 8.2.4831: crash when using maparg() and unmapping simplified keys

Problem:    Crash when using maparg() and unmapping simplified keys.
Solution:   Do not keep a mapblock pointer. (closes #10294)
diff --git a/src/version.c b/src/version.c
index 1c799d8..ba27532 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4831,
+/**/
     4830,
 /**/
     4829,