Error [] operator not supported for string in Plugin Tracker with itemId in URL

• Error

Hi Dev's!

First of all, sorry my english... Is not my natural language.

My fist post here!

I have another contribuition, but stay for another post. ;)

My setup:

Tiki 18.2
PHP 7.2.10-0ubuntu0.18.04.1
Linux 18.04 LTS

In a page with PLUGINTRACKER, if a itemID is passed in URL the follow error message is diplayed:

Fatal error: Uncaught Error: [] operator not supported for string

Cause:
In PHP 7+ (I cannot find exactly version) is more restritive in array initialization.

Source affected:
lib/wiki-plugins/wikiplugin_tracker.php

Solution:
In line 1498 the array $filter is initialized as string, and utilized as array, causing the error. Below the affected source snippet with corretion (line 1498)

1495 } elseif (! empty($itemId)) {
1496 if $fields) && empty($wiki) && empty($tpl {
1497 $fl = $fields;
1498 $filter = []; // $filter = ''; <- original
1499 foreach ($flds'data' as $f) {
1500 if (in_array($f'fieldId', $fl)) {
1501 $filter[] = $f;
1502 }
1503 }
1504 } else {

In my setup, after corretion the error do not more appear.

I hope have helped in something!

Salutes from Brazil!

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