patch 8.2.1971: memory leak when map() fails

Problem:    Memory leak when map() fails.
Solution:   Clear the typval.
diff --git a/src/version.c b/src/version.c
index 8cf37f0..91477bc 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1971,
+/**/
     1970,
 /**/
     1969,