patch 8.2.4168: disallowing empty function name breaks existing plugins

Problem:    Disallowing empty function name breaks existing plugins.
Solution:   Allow empty function name in legacy script.
diff --git a/src/version.c b/src/version.c
index 27ee162..cea8ece 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4168,
+/**/
     4167,
 /**/
     4166,