Fix Deprecation Warning for trim() Function in awkExistsAndRunsCorrec…

…tly() (#20969)

* Update Process.php

* Update: Use null-coalesce operator for null values

Co-authored-by: Michal Kleiner <mk@011.nz>

---------

Co-authored-by: Michal Kleiner <mk@011.nz>

core/CliMulti/Process.php

@@ -256,7 +256,7 @@ private static function psExistsAndRunsCorrectly()
     private static function awkExistsAndRunsCorrectly()
     {
         $testResult = @shell_exec('echo " 537 s000 Ss 0:00.05 login -pfl theuser /bin/bash -c exec -la bash /bin/bash" | ' . self::AWK_COMMAND . ' 2>/dev/null');
-        return trim($testResult) == '537';
+        return trim($testResult ?? '') == '537';
     }
 
     private static function isSystemNotSupported()