Fix PHP 8.1 "rawurlencode(null)" exception which blocks rendering a project page

Summary:
After PHP 8.1 the function rawurlencode() does not accept anymore the null value.

Thus return an empty string when the input parameter is null instead of passing the input parameter to rawurlencode().

Closes T15263

Test Plan:
Applied this change on top of D25144, D25145, D25146, D25147, D25151,
D25152, D25153 and D25163 and already existing Workboard located at
/project/view/1/ finally rendered in web browser.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: avivey, speck, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15263

Differential Revision: https://we.phorge.it/D25164