Better check antivirus sig available

cause the msg is not displayed in the GUI when no sigs are available.
From VT API: 

The API response format is a JSON object containing at least the following two properties:

response_code: if the item you searched for was not present in VirusTotal's dataset this result will be 0. If the requested item is still queued for analysis it will be -2. If the item was indeed present and it could be retrieved it will be 1. Any other case is detailed in the following sections.
verbose_msg: provides verbose information regarding the response_code property.
Whenever you exceed the public API request rate limit a 204 HTTP status code is returned.