patch 8.2.3246: memory use after free

Problem:    Memory use after free.
Solution:   When clearing a string option set the pointer to "empty_option".
diff --git a/src/version.c b/src/version.c
index 6b37200..7710018 100644
--- a/src/version.c
+++ b/src/version.c
@@ -756,6 +756,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3246,
+/**/
     3245,
 /**/
     3244,