If get-menu custom field for Page is declared as boolean above if condition should work
#if ($menu)
#if ($menu == true)
If it still does not work Check Database for ExpandoColumn table it will have your column name get-menu and default value if set.
ExpandoValue table will have actual value for your custom field, look for columnId that correspond your custom field and classPK which will be your page layout ID. This row will have your Value i.e. Either true / False.
If this row is present for your Page it should work in your VM code above.
Hope this helps you !