Fix various potential PHP 8.1 "strlen(null)" exceptions

Summary:
`strlen()` was used in Phabricator to check if a generic value is a non-empty string.
This behavior 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.

All lines changed in this patch had `Parameter #1 $string of function strlen expects string, string|null given` reported by PHPStan. Thus these should be safe to replace with `phutil_nonempty_string` as no calls care about the actual `strlen()` return value (length of a string).

Test Plan: Run static code analysis via `phpstan analyse -l 9`

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Differential Revision: https://we.phorge.it/D25778

src/applications/auth/adapter/PhutilBitbucketAuthAdapter.php

@@ -14,7 +14,7 @@ final class PhutilBitbucketAuthAdapter extends PhutilOAuth1AuthAdapter {
 
   public function getAccountURI() {
     $name = $this->getAccountID();
-    if (strlen($name)) {
+    if (phutil_nonempty_string($name)) {
       return 'https://bitbucket.org/'.$name;
     }
     return null;

src/applications/auth/adapter/PhutilGitHubAuthAdapter.php

@@ -31,7 +31,7 @@ final class PhutilGitHubAuthAdapter extends PhutilOAuthAuthAdapter {
 
   public function getAccountURI() {
     $name = $this->getAccountName();
-    if (strlen($name)) {
+    if (phutil_nonempty_string($name)) {
       return 'https://github.com/'.$name;
     }
     return null;

src/applications/auth/adapter/PhutilTwitterAuthAdapter.php

@@ -17,7 +17,7 @@ final class PhutilTwitterAuthAdapter extends PhutilOAuth1AuthAdapter {
 
   public function getAccountURI() {
     $name = $this->getAccountName();
-    if (strlen($name)) {
+    if (phutil_nonempty_string($name)) {
       return 'https://twitter.com/'.$name;
     }
     return null;

src/applications/diffusion/query/lowlevel/DiffusionLowLevelCommitQuery.php

@@ -126,11 +126,11 @@ final class DiffusionLowLevelCommitQuery
       $head = $parts[6];
       $tail = $parts[7];
 
-      if (strlen($head) && strlen($tail)) {
+      if (phutil_nonempty_string($head) && phutil_nonempty_string($tail)) {
         $body = $head."\n\n".$tail;
-      } else if (strlen($head)) {
+      } else if (phutil_nonempty_string($head)) {
         $body = $head;
-      } else if (strlen($tail)) {
+      } else if (phutil_nonempty_string($tail)) {
         $body = $tail;
       } else {
         $body = '';

src/infrastructure/markup/rule/PhabricatorKeyboardRemarkupRule.php

@@ -22,7 +22,7 @@ final class PhabricatorKeyboardRemarkupRule extends PhutilRemarkupRule {
     foreach ($keys as $k => $v) {
       $v = trim($v, " \n");
       $v = preg_replace('/\\\\(.)/', '\\1', $v);
-      if (!strlen($v)) {
+      if ($v === '') {
         unset($keys[$k]);
         continue;
       }