lib-mail: parse_addr_spec: Like in rfc822_skip_comment() check if las…

…t_comment is not NULL

This will fix possible NULL pointer dereference when caller does not set last_comment.

src/lib-mail/message-address.c

@@ -158,7 +158,8 @@ static int parse_addr_spec(struct message_address_parser_context *ctx)
 	/* addr-spec       = local-part "@" domain */
 	int ret, ret2;
 
-	str_truncate(ctx->parser.last_comment, 0);
+	if (ctx->parser.last_comment != NULL)
+		str_truncate(ctx->parser.last_comment, 0);
 
 	ret = parse_local_part(ctx);
 	if (ret != 0 && *ctx->parser.data == '@') {
@@ -167,9 +168,11 @@ static int parse_addr_spec(struct message_address_parser_context *ctx)
 			ret = ret2;
 	}
 
-	if (str_len(ctx->parser.last_comment) > 0) {
-		ctx->addr.name =
-			p_strdup(ctx->pool, str_c(ctx->parser.last_comment));
+	if (ctx->parser.last_comment != NULL) {
+		if (str_len(ctx->parser.last_comment) > 0) {
+			ctx->addr.name =
+				p_strdup(ctx->pool, str_c(ctx->parser.last_comment));
+		}
 	}
 	return ret;
 }