Fix fatal error in PHP8.x for invalid get data

[amieiro]

Problem

A malformed sort array throws a fatal error in PHP 8.x (in PHP 7.4 throws a warning).

Before this fix, if you add ?sort[by][foobar]=1 to a GlotPress URL, in a GET request, you will get an error 500.

Before

wget -S https://glotpress.test/glotpress/projects/local-plugins/glotpress/gl/default/\?sort\[by\]\[foobar\]\=1
...
HTTP request sent, awaiting response...
  HTTP/1.1 500 Internal Server Error

After

wget -S https://glotpress.test/glotpress/projects/local-plugins/glotpress/gl/default/\?sort\[by\]\[foobar\]\=1
...
HTTP request sent, awaiting response...
  HTTP/1.1 200 OK

Fixes #1753.

Solution

The malformed URL throws an error at wp-content/plugins/GlotPress/gp-includes/misc.php on line 66 because the $key parameter in the gp_array_get() function is an array. This PR checks if the $key is a string or a number before using it as key in the array.

After solving this first problem, it arises another warning:

PHP Warning:  Array to string conversion in wp-content/plugins/GlotPress/gp-templates/translations.php on line 135
PHP Warning:  Array to string conversion in wp-content/plugins/GlotPress/gp-templates/translations.php on line 149
PHP Warning:  Array to string conversion in wp-content/plugins/GlotPress/gp-templates/translations.php on line 163
PHP Warning:  Array to string conversion in wp-content/plugins/GlotPress/gp-templates/translations.php on line 177
PHP Warning:  Array to string conversion in wp-content/plugins/GlotPress/gp-templates/translations.php on line 191
PHP Warning:  Array to string conversion in wp-content/plugins/GlotPress/gp-templates/translations.php on line 207
PHP Warning:  Array to string conversion in wp-content/plugins/GlotPress/gp-templates/translations.php on line 221

This problem is solved removing the values from the filters that are not strings or numbers.

[trymebytes]

I left a tiny comment but looks good to me!