Items using: "web.page.*" switch to unsupported when checked service is unavailable

Steps to reproduce:

1. Create item using web.page.get or web.page.regexp and configure checking of some working service (eg. localhost, YOUR_SERVICE:PORT, "REGEXP")
2. Check that item is properly updated in zabbix.
3. Stop your service.
4. Check item value in zabbix.

Result:
Item will come unsupported with error message: 

"HTTP get error: cannot connect to [[localhost]:PORT]: [111] Connection refuse"

 
Expected:
Item should get empty string value (like it works in zabbix-agent with version 3.0.3)

Workaround:

Downgrade zabbix-agent to 3.0.3 version.