patch 8.2.1278: Vim9: line break after "->" only allowed in :def function

Problem:    Vim9: line break after "->" only allowed in :def function.
Solution:   Only allow line break after "->". (closes #6492)
diff --git a/src/globals.h b/src/globals.h
index 5e2306b..77c3641 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1730,6 +1730,7 @@
 EXTERN char e_toomsbra[]	INIT(= N_("E76: Too many ["));
 EXTERN char e_toomany[]	INIT(= N_("E77: Too many file names"));
 EXTERN char e_trailing[]	INIT(= N_("E488: Trailing characters"));
+EXTERN char e_trailing_arg[]	INIT(= N_("E488: Trailing characters: %s"));
 EXTERN char e_umark[]		INIT(= N_("E78: Unknown mark"));
 EXTERN char e_wildexpand[]	INIT(= N_("E79: Cannot expand wildcards"));
 EXTERN char e_winheight[]	INIT(= N_("E591: 'winheight' cannot be smaller than 'winminheight'"));