Issue when using cache

I am using Last Codeigniter 3.1.3 and i have a issue with cache

I am using cache like this:

PHP Code:

$key = "_sys_categories_";
        $how_much = 3600;
        $categories = array();
        if ( !$categories = $this->cache->file->get( $key ) ) {
            $categories = $this->category->read_all( array('status' => 1) );
            $this->cache->file->save( $key, $categories, $how_much );
        } 


I receive this Warning:

[2017-04-05 00:00:04][E/codeigniter][URI=/apis/get/csv] Severity: Warning --> file_get_contents(application/cache/_sys_categories_): failed to open stream: No such file or directory /system/libraries/Cache/drivers/Cache_file.php 275

How to handle it?

In another place and for another cache i receive also this Warning

Severity: Warning --> file_get_contents(application/cache/_sys_properties_searchable_): failed to open stream: Stale file handle /system/libraries/Cache/drivers/Cache_file.php 275

Can you help me ?