patch 8.2.4111: potential proglem when map is deleted while executing

Problem:    Potential proglem when map is deleted while executing.
Solution:   Reset last used map pointer when deleting a mapping.

src/map.c

@@ -85,6 +85,9 @@ map_free(mapblock_T **mpp)
     vim_free(mp->m_orig_str);
     *mpp = mp->m_next;
     vim_free(mp);
+#ifdef FEAT_EVAL
+    reset_last_used_map();
+#endif
 }
 
 /*

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4111,
 /**/
     4110,
 /**/