Fix to just check if plugin is there

postinstall.pl

@@ -7,7 +7,7 @@
 sub module_install
 {
 # Enable virtualmin-htpasswd module once
-if (&virtual_server::plugin_defined("virtualmin-nginx", "start_nginx")) {
+if (&indexof('virtualmin-nginx', @virtual_server::plugins) >= 0) {
     if ($virtual_server::config{'plugins'} !~ /$module_name/ &&
         $virtual_server::config{'plugins_postinstall_enabled'} !~ /$module_name/) {
         &virtual_server::lock_file($virtual_server::module_config_file);