Update main.php humanize_usage_size() (#4015)

* Update main.php humanize_usage_size()

Tweak humanize_usage_size() so that it doesn't die part way through with:

2023/09/21 14:18:16 [error] 353479#0: *56 FastCGI sent in stderr: "PHP message: PHP Fatal error:  Uncaught TypeError: number_format(): Argument #1 ($num) must be of type float, string given in /usr/local/hestia/web/inc/main.php:368
Stack trace:
#0 /usr/local/hestia/web/inc/main.php(368): number_format()
#1 /usr/local/hestia/web/templates/pages/list_user.php(246): humanize_usage_size()
#2 /usr/local/hestia/web/inc/main.php(202): include('...')
#3 /usr/local/hestia/web/list/user/index.php(33): render_page()
#4 {main}
  thrown in /usr/local/hestia/web/inc/main.php on line 368" while reading upstream, client: 81.174.134.33, server: _, request: "GET /list/user/ HTTP/2.0", upstream: "fastcgi://unix:/run/hestia-php.sock:", host: "brian2022.newbyhost.com:9183", referrer: "https://brian2022.newbyhost.com:9183/list/web/"

For some reason some stats come back as null, which breaks this function

web/inc/main.php

@@ -341,6 +341,9 @@ function humanize_usage_size($usage, $round = 2) {
 	if ($usage == "unlimited") {
 		return "∞";
 	}
+	if ($usage < 1) {
+		$usage = "0";
+	}	
 	$display_usage = $usage;
 	if ($usage > 1024) {
 		$usage = $usage / 1024;