Spelling mistake in previous commit..

db/install.php

@@ -61,7 +61,7 @@ function xmldb_qtype_stack_install() {
         set_config('castimeout', 10, 'qtype_stack');
         set_config('casresultscache', 'db', 'qtype_stack');
         set_config('maximacommand', '', 'qtype_stack');
-        set_config('maximacommandop', '', 'qtype_stack');
+        set_config('maximacommandopt', '', 'qtype_stack');
         set_config('maximacommandserver', '', 'qtype_stack');
         set_config('serveruserpass', '', 'qtype_stack');
         set_config('plotcommand', '', 'qtype_stack');