Plugin search query broken after deletion

[gluten]

When searching on the network admin plugins page on version 3.1.1, and then deleting a plugin the search query appears to lose any spaces. For example, if I search for "Javascript to Footer" to find a plugin that is no longer needed:

1. Click "delete" on my desired plugin
2. I am taken to a delete confirmation screen with the url: /wp-admin/network/plugins.php?action=delete-selected&checked%5B0%5D=footer-javascript%2Ffooter-javascript.php&plugin_status=search&paged=1&s=JavaScript+to+Footer
3. I click to delete the plugin
4. I am redirected to: /wp-admin/network/plugins.php?deleted=true&plugin_status=search&paged=1&s=JavaScripttoFooter

The spaces were preserved up until I click delete and and redirected, at which point they are somehow lost. I have been able to confirm this bug on two separate wordpress multisite installs.

#16548