Fix a PHP 8.1 deprecated use of strlen with a NULL argument

Summary:
This call prevents users to view a commit in subversion repositories
Indeed, if commiter and/or author field is not properly defined strlen is call with a NULL argument.
Using strlen to check string validity is deprecated since PHP 8.1, phorge adopts phutil_nonempty_string() as a replacement.

Note: this may highlight other absurd input values that might be worth correcting
instead of just ignoring. If phutil_nonempty_string() throws an exception in your
instance, report it to Phorge to evaluate and fix that specific corner case.

Fix T15610

Test Plan:
- Sign in (if needed)
- Open a diffusion SVN repository
- Open a commit without user name and or email
- You should be able to view the commit

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15610

Differential Revision: https://we.phorge.it/D25400

src/applications/repository/storage/PhabricatorRepositoryCommit.php

@@ -478,7 +478,7 @@ final class PhabricatorRepositoryCommit
     }
 
     $author = $this->getRawAuthorStringForDisplay();
-    if (strlen($author)) {
+    if (phutil_nonempty_string($author)) {
       return DiffusionView::renderName($author);
     }
 
@@ -493,7 +493,7 @@ final class PhabricatorRepositoryCommit
     }
 
     $committer = $this->getRawCommitterStringForDisplay();
-    if (strlen($committer)) {
+    if (phutil_nonempty_string($committer)) {
       return DiffusionView::renderName($committer);
     }
 

src/applications/repository/storage/PhabricatorRepositoryCommitData.php

@@ -131,7 +131,7 @@ final class PhabricatorRepositoryCommitData extends PhabricatorRepositoryDAO {
     $ref = $this->getCommitRef();
 
     $committer = $ref->getCommitter();
-    if (strlen($committer)) {
+    if (phutil_nonempty_string($committer)) {
       return $committer;
     }