Disconnect while downloading

Previously if a disconnect occured while downloading a non recoverable error was displayed. This PR attempts to fix this by making sure `request_completed` signal is emitted with an `STATUS_CONNECTION_ERROR` response code.

scene/main/http_request.cpp

@@ -349,6 +349,8 @@ bool HTTPRequest::_update_connection() {
 			}
 
 			client->poll();
+			if (client->get_status() != HTTPClient::STATUS_BODY)
+				break; // State changed after this poll, will check at next iteration.
 
 			PoolByteArray chunk = client->read_response_body_chunk();
 			downloaded += chunk.size();