Generated function graph svg is empty

[lighthuter]

I have a profile generated by https://github.com/reliforp/reli-prof and converted to callgrind format. This file works perfectly with qcachegrind, but svg generated by webcache is empty

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
 "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<!-- Generated by graphviz version 2.43.0 (0)
 -->
<!-- Title: %3 Pages: 1 -->
<svg width="8pt" height="8pt"
 viewBox="0.00 0.00 8.00 8.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 4)">
<title>%3</title>
<polygon fill="white" stroke="transparent" points="-4,4 -4,-4 4,-4 4,4 -4,4"/>
</g>
</svg>

Profile has structure like this:

# format callgrind
events: Samples

fl=/data/vendor/graham-campbell/result-type/src/Success.php
fn=GrahamCampbell\ResultType\Success::flatMap
93 1
cfl=/data/vendor/vlucas/phpdotenv/src/Parser/EntryParser.php
cfn=Dotenv\Parser\EntryParser::{closure}(/data/vendor/vlucas/phpdotenv/src/Parser/EntryParser.php:51-58)
calls=-1 -1
93 1
cfl=/data/vendor/vlucas/phpdotenv/src/Parser/Parser.php
cfn=Dotenv\Parser\Parser::{closure}(/data/vendor/vlucas/phpdotenv/src/Parser/Parser.php:46-48)
calls=-1 -1
93 1
cfl=/data/vendor/vlucas/phpdotenv/src/Loader/Resolver.php
cfn=Dotenv\Loader\Resolver::{closure}(/data/vendor/vlucas/phpdotenv/src/Loader/Resolver.php:40-42)
calls=-1 -1
93 1
cfl=/data/vendor/vlucas/phpdotenv/src/Loader/Loader.php
cfn=Dotenv\Loader\Loader::{closure}(/data/vendor/vlucas/phpdotenv/src/Loader/Loader.php:26-45)
calls=-1 -1
93 1

Is this format supported by webgrind? Am I doing something wrong?