add check for empty shell

Author: simonLeary42

resources/lib/UnityUser.php

@@ -453,6 +453,9 @@ public function setLoginShell($shell, $operator = null, $send_mail = true)
         if ($shell != trim($shell)) {
             throw new Exception("leading/trailing whitespace is not allowed in a login shell!");
         }
+        if (empty($shell)) {
+            throw new Exception("login shell must not be empty!");
+        }
         $ldapUser = $this->getLDAPUser();
         if ($ldapUser->exists()) {
             $ldapUser->setAttribute("loginshell", $shell);

test/functional/LoginShellSetTest.php

@@ -33,10 +33,11 @@ public function testSetLoginShellCustom(string $shell): void
     {
         global $USER;
         // FIXME add check to avoid warning from ldap_modify
-        if (!mb_check_encoding($shell, 'ASCII')) {
-            $this->expectException("Exception");
-        }
-        if ($shell != trim($shell)) {
+        if (
+            (!mb_check_encoding($shell, 'ASCII')) ||
+            ($shell != trim($shell)) ||
+            (empty($shell))
+        ) {
             $this->expectException("Exception");
         }
         // FIXME shell is not validated