patch 8.2.2266: Vim9: it can be hard to see where white space is missing

Problem:    Vim9: it can be hard to see where white space is missing.
Solution:   Mention the text where the error was seen. (closes #7580)
diff --git a/src/evalvars.c b/src/evalvars.c
index 9f84d76..346031e 100644
--- a/src/evalvars.c
+++ b/src/evalvars.c
@@ -863,7 +863,8 @@
 						   || !IS_WHITE_OR_NUL(*expr)))
 	    {
 		vim_strncpy(op, expr - len, len);
-		semsg(_(e_white_space_required_before_and_after_str), op);
+		semsg(_(e_white_space_required_before_and_after_str_at_str),
+								   op, argend);
 		i = FAIL;
 	    }