Typically encountered with a custom plugin, a GET parameter containing 0 is left out of the array. Consider the following example:

As an example URL:
/admin/plugin/myplugin/admin_forms/fields/0/lookup/51

get[] array contains:
get[0] = lookup
get[1] = 51

However, this example URL works as expected:
/admin/plugin/myplugin/admin_forms/fields/15/lookup/1096

get[] array contains:
get[0] = 15
get[1] = 'lookup'
get[2] = 1096

Basically the value 0 does not exist in the array, but if a non-zero value is provided, it is included in GET.

Jono suggested the following fix:

vendors/minphp/bridge/lib/Router.php around line 330 change

            // Only assign GET parameters that are not query parameters
            if (empty($part) || substr($part, 0, 1) === '?') {
                continue;
            }

To

            // Only assign GET parameters that are not query parameters
            if ($part === '' || $part === null || substr($part, 0, 1) === '?') {
                continue;
            }

NOTE! Customer stated that this was not sufficient, and suggested the following:

Also had to do something similar near line 276 of same method:

// Begin building URI
for ($i = count($pathParts)1; $i >= 0; $i-) {
//if (!empty($pathParts[$i])) {
if ($pathParts[$i] != '' && $pathParts[$i] != null)

}

So with the edit suggested at line 330 and the edit above near line 276, the 0 is not skipped. I loaded several admin area pages and client area pages following these edits and it does not appear to have broken other pages loading.