PM2.5 Value is updating even without sensor connection

[kumarrishav]

STR :

1. Do all the proper connection so that PM2.5 start updating on dashboard.
2. Once you get it working properly, Now remove TX-RX wire connection.
3. Now check the dashboard. You will find that it's still uploading the PM2.5 data (which i suppose is wrong).
4. Now remove GND and Vin wire connection. You will find, still PM2.5 data is uploading on sensorweb server (kind of weird?). Without sensor connection, how it can get PM2.5 data?

@evanxd @yshlin