patch 8.2.2846: Vim9: "echo Func()" does not give an error for using void

Problem:    Vim9: "echo Func()" does not give an error for a function without
            a return value.
Solution:   Give an error.  Be more specific about why a value is invalid.
diff --git a/src/errors.h b/src/errors.h
index 3d12c1d..2a0a536 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -31,6 +31,8 @@
 	INIT(= N_("E719: Cannot slice a Dictionary"));
 EXTERN char e_assert_fails_second_arg[]
 	INIT(= N_("E856: \"assert_fails()\" second argument must be a string or a list with one or two strings"));
+EXTERN char e_using_invalid_value_as_string_str[]
+	INIT(= N_("E908: using an invalid value as a String: %s"));
 EXTERN char e_cannot_index_special_variable[]
 	INIT(= N_("E909: Cannot index a special variable"));
 #endif
@@ -409,3 +411,5 @@
 	INIT(= N_("E1185: Cannot nest :redir"));
 EXTERN char e_missing_redir_end[]
 	INIT(= N_("E1185: Missing :redir END"));
+EXTERN char e_expression_does_not_result_in_value_str[]
+	INIT(= N_("E1186: Expression does not result in a value: %s"));