Custom Reports issue

Hi,
I was followed “Custom Reports Extend” guide. But when I implement the API method like example. I got the error like this:

Oops… there was a problem during the request. Maybe the server had a temporary issue, or maybe you requested …

When I try to use var_dump() to debug I got error message like:

A fatal error occurred
The following error just broke Matomo (v3.6.0-b1): in D:\Project\MyMatomo\core\Plugin\Visualization.php line 362

Then I followed troubleshooting guide Matomo give me and also follow
https://matomo.org/faq/troubleshooting/faq_19489/
I saw the errorlog

[Thu Aug 02 15:24:49.087802 2018] [authz_core:error] [pid 17144:tid 1892] [client 127.0.0.1:58863] AH01630: client denied by server configuration: D:/Project/MyMatomo/plugins/Morpheus/icons/dist/browsers, referer: http://mymatomo.test/index.php?module=CoreHome&action=index&idSite=1&period=day&date=yesterday
[Thu Aug 02 15:24:49.094797 2018] [authz_core:error] [pid 17144:tid 1936] [client 127.0.0.1:58864] AH01630: client denied by server configuration: D:/Project/MyMatomo/plugins/Morpheus/icons/dist/os, referer: http://mymatomo.test/index.php?module=CoreHome&action=index&idSite=1&period=day&date=yesterday
[Thu Aug 02 15:24:49.097796 2018] [authz_core:error] [pid 17144:tid 1896] [client 127.0.0.1:58865] AH01630: client denied by server configuration: D:/Project/MyMatomo/plugins/Morpheus/icons/dist/devices, referer: http://mymatomo.test/index.php?module=CoreHome&action=index&idSite=1&period=day&date=yesterday

But all log error is about missing the icon in Morpheus plugin (I has checked the folder and don’t see any subfolder of icons folder)

So what is the problem here? And how do I solved it?
Thanks a lot!