patch 8.2.1773: crash when calling mapset() with a list as first argument

Problem:    Crash when calling mapset() with a list as first argument.
Solution:   Check for NULL. (closes #7040)
diff --git a/src/version.c b/src/version.c
index d5c8f30..acac541 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1773,
+/**/
     1772,
 /**/
     1771,